Blue Sea 7611 or 7622?
- Thread starter Jsweezy
- Start date
NW40
Explorer
Using the yellow switch on the ACR, you can leave the unit in Auto mode and let it use its built in logic (combines the batteries when they are being charged, and isolates batteries when there's no charging source, i.e., alternator, solar panels, shore power).
Or flipping the switch the other way, you permanently isolate the batteries regardless of logic. I use this when I'm topping off each battery at home with a battery tender.
There's also a temporary (~15 minutes) third option which allows you combine the batteries regardless of charging state. You could use this mode for jumping your starting battery from the aux battery, or winching with both batteries in a worst case scenario (truck is not running, but you need to get it out of the situation it's in, even if it means possibly killing both batts).
Or flipping the switch the other way, you permanently isolate the batteries regardless of logic. I use this when I'm topping off each battery at home with a battery tender.
There's also a temporary (~15 minutes) third option which allows you combine the batteries regardless of charging state. You could use this mode for jumping your starting battery from the aux battery, or winching with both batteries in a worst case scenario (truck is not running, but you need to get it out of the situation it's in, even if it means possibly killing both batts).
Another way to look at this is to use the 7611 or the even cheaper mACR (<$50) and add a heavy duty battery switch in parallel (< $20), or carry jumper cables, for the off chance you need to self jump. You really don't need a 100A+ rated relay for charging and accessory loads. If you have or want a winch it maybe a different story.
dstock
Explorer
I have the 7622. The remote switch is great, the mechanical yellow switch is redundant but I like it for when I take the Jeep in for service, so I can completely lock out the aux battery and the accessories tied to it.
I did self-jump from the driver's seat the other day via the remote switch when my starting battery gave up the ghost, it was very nice indeed!
I did self-jump from the driver's seat the other day via the remote switch when my starting battery gave up the ghost, it was very nice indeed!
DiploStrat
Expedition Leader
I would disagree, strongly. When I am 100 - 200A down, I want the biggest, baddest charge I can get. The Lifeline manual calls for up to 5C, which in my case would be 5x600A. With only a 250A alternator, I won't ever approach that, but I routinely see charge rates of well over 150A.
NW40
Explorer
The Blue Sea ACR will still operate as designed in terms of battery combining/isolating based on charge state, but your batteries won't be optimally charged. I experienced this on my FJ40 when I installed a starting batt and a much larger deep cycle batt. My understanding now is that batteries of different types, size, or even age shouldn't be combined and charged on the same circuit. One battery will draw the other down unless they are of the same size, type, and age. No relay will overcome this limitation. You can do it anyways (and many do), but it's not ideal and your batteries will wear out quicker. After I learned this with my FJ40 (by experience and after doing more research), I bought two of the same Diehard Platinum Marine batteries for my Land Rover Discovery.
I think there are charge controllers out there which provide separate regulation for two batteries. I couldn't point you in the right direction for that, though.
I think there are charge controllers out there which provide separate regulation for two batteries. I couldn't point you in the right direction for that, though.
patoz
Expedition Leader
I'm in the process of installing a winch and dual battery system on my F250 right now, and I will be using the 7622 without a doubt. As already mentioned, it's only a few dollars more and having the ability to manually connect the two batteries is well worth it to me. Dash mounted winch controls are an absolute must for me also.
If you wire it according to the Blue Sea diagram, power for the switching process is coming from the house battery. So theoretically, if the house battery doesn't have enough power to activate the switch, then it doesn't have enough power to jump off the starting battery either. But what if the problem is just a blown fuse or a corroded or frayed control wire? These things always seem to present themselves at the most inopportune times, like winching during a water crossing or while stuck in a deep mud hole, etc. Having that manual switch can make the difference in making it back to camp or playing submarine commander!
The only difference in the two is the manual switch, as you can see here.
Good luck, but always prepare for the worse case scenario!
If you wire it according to the Blue Sea diagram, power for the switching process is coming from the house battery. So theoretically, if the house battery doesn't have enough power to activate the switch, then it doesn't have enough power to jump off the starting battery either. But what if the problem is just a blown fuse or a corroded or frayed control wire? These things always seem to present themselves at the most inopportune times, like winching during a water crossing or while stuck in a deep mud hole, etc. Having that manual switch can make the difference in making it back to camp or playing submarine commander!
The only difference in the two is the manual switch, as you can see here.
Good luck, but always prepare for the worse case scenario!
The old myth of mismatched batteries rears it's ugly head. It's still incorrect information in this circumstance.
12 volt Batteries that are in parallel, and only when charging, can be as mismatched as you want. They will be fine. It's because the charging voltage is above the float voltage of both batteries, so no discharging of one into the other can occur. They are also protected during discharge by the ACR, which opens when the charge current is removed and isolates the batteries.
When you have a bank of batteries, like in an RV, then it's important that all the batteries are the same.
For very simple systems like most of us, with 2 batteries in parallel, but isolated, the ACRs are ideal. Just pick whether you want more features or less. The batteries do not have to be the same. As long as they are 6 cell 12 volt batteries, they will be fine.
DiploStrat
Expedition Leader
Some Comments
If I may:
-- A relay is nothing but a remote control switch. It does not charge anything, it merely makes or breaks a circuit. A relay can be controlled by a switch or some form of automatic controller. A relay needs to be heavy enough to carry the maximum current in a circuit without failing.
-- A voltage sensing relay is one that opens and closes in response to the voltage passing through the relay. Most sense the voltage on either side of the relay, but you could design one that reads only one side. Most incorporate some additional intelligence such as a time delay to reduce the chances of the relay opening or closing too soon or too often.
-- In a typical battery charging scenario for a 12v circuit the relay will close (make contact) when it detects 13v or more. The exact voltage may be adjustable and, as noted, there may be a time delay to assure that the voltage is stable at 13v or more. If the relay detects that the voltage has dropped to 12.7v, then the relay will open. 12.7v is the typical "full charge" voltage for a "12 volt" battery. Again, some models are adjustable. The Australians, for example, sell some with a "winch mode" which is intended to stay connected even when the voltage drops to 12.5v under the load of a winch. (I think a dash switch is a better idea.) The relay may also incorporate catastrophic high and low voltage cutouts - typically over 16v or below 11v.
-- The batteries within a given battery bank, that is batteries that are permanently connected together, whether in series or parallel, when both charging and discharging, should match exactly. Even to sequential serial numbers if you can arrange it.
-- Batteries that are only connected when under charge, as for example a typical set up on a yacht, RV, or narrowboat do not have to match in size. In fact, they will almost never match in size. In a properly designed system, for example one controlled by the ignition switch or by an intelligent voltage sensing relay, there is no need to worry about a size imbalance because as soon as the ignition key is "off" or as soon as either battery drops back to a "full" charge, the relay will open keeping the batteries isolated from each other.
-- Batteries and their chargers do have to match. Typically, a deep cycle AGM battery (e.g. Lifeline) calls for a charge voltage of 14.4v at 20C/70F. An open cell deep cycle battery (e.g. Trojan) calls for around 14.8v. This means that if you are going to use a relay based system, then your camper/house battery should have have grossly the same voltage requirements as you starter battery, or, more properly, the output of your vehicle's alternator/regulator combination. If they do not match, then you will need to compensate.
-- Many modern vehicles come from the factory with some form of AGM battery and easily produce the required 14.4v. (The exact voltage should vary with temperature.) There are some exceptions - many Toyotas only produce 13.9v and some Sprinters will reach, but not remain at 14v+. In this case you may have problems with a relay based system.
-- There are several options if your vehicle cannot produce the required voltage:
1) Raise the alternator to the desired level. In many cases this is easily done through an aftermarket adjustor by by replacing a diode. (The latter trick being popular in Australia with Toyotas.) This is what Expo member "skygear" does with his Toyota.
2) Use a Battery to Battery charger such as made by Sterling Power or CTEK. This allows you to run a different charging voltage to each battery bank.
3) Make up the difference with a solar or shore charger. Obviously, your charge will be slower if your alternator is putting out 13.9v as opposed to 14.4v, but if your solar charger is putting out a full 14.4v you will still achieve a complete charge.
CTEK, for example sells two components, the D250S and the SmartPass which are designed to work together. When the camper battery is deeply discharged, the system closes a relay rated at 80A to allow direct connection between the starter and camper batteries. As the camper battery charges and the charge rate drops to 20A, then the relay opens and the battery to battery charger finishes the charge, boosting the charge voltage to the desired level. (The unit also includes a small solar controller.)
Some final notes:
-- All charging systems require properly sized wiring to assure a fast charge. If the wiring is too small, then the transfer of current will be very slow, leading to the old camper's tale: "You can't charge your camper battery from the engine." Yes, you can, but it may take forever. Once you get into the 1 AWG range, voltage drop becomes less and less of an issue, because as the charge rate drops, the voltage drop reduces as well. Thus you can design a very effective system that appears to be slightly undersized.
-- Lead Acid batteries require a long, long absorb cycle. Much longer than most of us will ever drive during a given day, thus most of the worry about a true float is irrelevant when charging from the engine. A greater need is solar or shore power to complete the charge.
-- Lithium is different.
If I may:
-- A relay is nothing but a remote control switch. It does not charge anything, it merely makes or breaks a circuit. A relay can be controlled by a switch or some form of automatic controller. A relay needs to be heavy enough to carry the maximum current in a circuit without failing.
-- A voltage sensing relay is one that opens and closes in response to the voltage passing through the relay. Most sense the voltage on either side of the relay, but you could design one that reads only one side. Most incorporate some additional intelligence such as a time delay to reduce the chances of the relay opening or closing too soon or too often.
-- In a typical battery charging scenario for a 12v circuit the relay will close (make contact) when it detects 13v or more. The exact voltage may be adjustable and, as noted, there may be a time delay to assure that the voltage is stable at 13v or more. If the relay detects that the voltage has dropped to 12.7v, then the relay will open. 12.7v is the typical "full charge" voltage for a "12 volt" battery. Again, some models are adjustable. The Australians, for example, sell some with a "winch mode" which is intended to stay connected even when the voltage drops to 12.5v under the load of a winch. (I think a dash switch is a better idea.) The relay may also incorporate catastrophic high and low voltage cutouts - typically over 16v or below 11v.
-- The batteries within a given battery bank, that is batteries that are permanently connected together, whether in series or parallel, when both charging and discharging, should match exactly. Even to sequential serial numbers if you can arrange it.
-- Batteries that are only connected when under charge, as for example a typical set up on a yacht, RV, or narrowboat do not have to match in size. In fact, they will almost never match in size. In a properly designed system, for example one controlled by the ignition switch or by an intelligent voltage sensing relay, there is no need to worry about a size imbalance because as soon as the ignition key is "off" or as soon as either battery drops back to a "full" charge, the relay will open keeping the batteries isolated from each other.
-- Batteries and their chargers do have to match. Typically, a deep cycle AGM battery (e.g. Lifeline) calls for a charge voltage of 14.4v at 20C/70F. An open cell deep cycle battery (e.g. Trojan) calls for around 14.8v. This means that if you are going to use a relay based system, then your camper/house battery should have have grossly the same voltage requirements as you starter battery, or, more properly, the output of your vehicle's alternator/regulator combination. If they do not match, then you will need to compensate.
-- Many modern vehicles come from the factory with some form of AGM battery and easily produce the required 14.4v. (The exact voltage should vary with temperature.) There are some exceptions - many Toyotas only produce 13.9v and some Sprinters will reach, but not remain at 14v+. In this case you may have problems with a relay based system.
-- There are several options if your vehicle cannot produce the required voltage:
1) Raise the alternator to the desired level. In many cases this is easily done through an aftermarket adjustor by by replacing a diode. (The latter trick being popular in Australia with Toyotas.) This is what Expo member "skygear" does with his Toyota.
2) Use a Battery to Battery charger such as made by Sterling Power or CTEK. This allows you to run a different charging voltage to each battery bank.
3) Make up the difference with a solar or shore charger. Obviously, your charge will be slower if your alternator is putting out 13.9v as opposed to 14.4v, but if your solar charger is putting out a full 14.4v you will still achieve a complete charge.
CTEK, for example sells two components, the D250S and the SmartPass which are designed to work together. When the camper battery is deeply discharged, the system closes a relay rated at 80A to allow direct connection between the starter and camper batteries. As the camper battery charges and the charge rate drops to 20A, then the relay opens and the battery to battery charger finishes the charge, boosting the charge voltage to the desired level. (The unit also includes a small solar controller.)
Some final notes:
-- All charging systems require properly sized wiring to assure a fast charge. If the wiring is too small, then the transfer of current will be very slow, leading to the old camper's tale: "You can't charge your camper battery from the engine." Yes, you can, but it may take forever. Once you get into the 1 AWG range, voltage drop becomes less and less of an issue, because as the charge rate drops, the voltage drop reduces as well. Thus you can design a very effective system that appears to be slightly undersized.
-- Lead Acid batteries require a long, long absorb cycle. Much longer than most of us will ever drive during a given day, thus most of the worry about a true float is irrelevant when charging from the engine. A greater need is solar or shore power to complete the charge.
-- Lithium is different.
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Great information! Thanks to all. I'm looking at the ACR 7728 for a particular reason: My Jeep has a Deka AGM starting battery. My house bank is 2 Lifeline 6v's in series. At 12V the rated capy is 300A. At a 50% DoD, I will need to replace 150A. My solar system will on paper input 23A/hr x ~5 hrs. I'm considering an alternator source for times when I need electricity in cloudy weather or night. Plus, it seems wasteful to be driving with a full starting battery and the alternator has Amps to spare.
I know the alternator will never get me past absorption at 13.5. I'm counting on the solar to finish getting me to float. I'm just thinking when my house bank is discharged 150A, the alternator (assuming I've broken camp and am travelling) will replinish the bank quicker.
I have metering equipment in the house system thatets me see its state of charge and % of recharge. So, I'm thinking if i monitor that well while driving, I might get by without a 7728. I own a Perko 1-2-both-off switch. I guess the risk wo the automatic isolator is running the alternator too jard for too long.
Given my 160A OE alternator and the size of my house bank, and 12' between the isolator' location and the house Pos buss bar, what size cable do I need for the Pos run?
I know the alternator will never get me past absorption at 13.5. I'm counting on the solar to finish getting me to float. I'm just thinking when my house bank is discharged 150A, the alternator (assuming I've broken camp and am travelling) will replinish the bank quicker.
I have metering equipment in the house system thatets me see its state of charge and % of recharge. So, I'm thinking if i monitor that well while driving, I might get by without a 7728. I own a Perko 1-2-both-off switch. I guess the risk wo the automatic isolator is running the alternator too jard for too long.
Given my 160A OE alternator and the size of my house bank, and 12' between the isolator' location and the house Pos buss bar, what size cable do I need for the Pos run?