Watts this? I'm amped!

[007]

http://www.traxide.com.au/isolators/usi-160---160-amp-winch.html



I'm trying to figure out my next dual battery setup, to do this I am inviting everyone to hash this out in an old fashioned throw-down debate. The last setup standing will have the honor of keeping my beer cold:beer:

I'm going to make the case for the Traxide USI-160 ultra smart isolator first. This module has several modes -ISOLATE (disconnects batts, below 12.6) SHARED (disconnects below 12v)JUMP START and WINCH (combines with motor running to 10v)

I'm thinking this device may be the ticket for a large dual battery setup. I like that it keeps starter and house battery combined until the starter battery hits a preset voltage, and then it isolates (separates). My national Luna system disconnects as soon as its not charging, which is good, but I don't get automatic access to that huge starter battery under the hood, even though it has enough capacity to start my truck 25 times in a row.

I look at it this way - if you are going to purchase 2 new large deep cycle batteries (starter & house), you should take advantage of all that capacity. If I'm going to camp in isolation for 3 weeks without a solar charger, maybe I would keep it in ISOLATE MODE, to insure a fresh starting battery in three weeks time.

The Traxide Isolator has a setting to operate in the above manner, but also allow a different type of use. This use is called "shared", meaning that the two batteries stay connected until the starter battery hits 12volts - then it isolates. Now I'm sure many of you think, 12v is way to low for a starting battery to discharge, but I have never had any trouble starting my truck with a large group 31 battery at 12volts. But to be fair 12volts is about 50% capacity, and if your battery is really small, or old, or you have a diesel, this could get sketchy.

Well why would you want your starting battery to be allowed to drain up to 50% capacity in shared mode?

1. More capacity - It allows you to use 50% of your starting battery for house needs, this essentially doubles your usable battery capacity for accesories. When I pay over $500 for a set deep cycle batteries, I want to use them! Having a group 31 battery just to run a starter seems like a waste most of the time.

2. Minimize big discharges - It saves my house battery from a beating, both batteries share the load. So instead of a house battery getting discharged to say 50% - Both batteries would get discharged only 25% (leaving 75% capacity ea). The key to battery life is minimizing big discharges and maximizing fast recharges. I think most recharging systems will bring two batteries up from 75% capacity to 95% capacity, faster than one battery from 50% to 95%. One battery can't absorb the full capacity of the alternator like two can.

3. Harmony - the two batteries will spend most of their lives combined in an equalized state, charging and discharging together. I'm no expert, but I would think its better for the batteries to not be dumping into each other with large differences in charge.

4. Charging simplicity - again, I'm no expert, but I would think smart chargers and solar chargers would have an easier time sensing which state of charge the batteries are in when they are at the same voltage from being equalized all the time. The charger is less likely to get confused by the other batteries voltage if they are the same.

5. Battery life - I purchase and replace my dual batteries in sets. When one battery is at the end of its life, I'm not going to replace it with one battery, I'm replacing both. The Traxide setup seems like it would keep the house battery and the starter battery at more equal life spans.

So that's my case for the Traxide USI-160

I may be way off base, so I want to hear your take on things, please discuss.

 

[DiploStrat]

Looks Great

The Traxide looks like an interesting option for a smaller system (Group 31 is small and 160A is low) where you need to squeeze out every last amp. Assuming a 100Ah deep cycle battery paired with a 100 Ah starting battery, dropping the disconnect voltage to 12v might let you get 75Ah out of the system; maybe even 100Ah if you had a healthy alternator and were sure that you would run the engine for several hours the next day. This might be a nice package for a two-batteries-under-the-hood setup.

The real issue is, how much current do you need and how long do you need it. For a "camper" with a small cooler, lights, and a fan, 75Ah might well be enough for one day. In may case, call it a "motor home," I budgeted for 150Ah per day, for three days. This means a much, much bigger battery bank, and a much larger current flow. For these applications I would recommend a Blue Sea ACR, like this: http://www.bluesea.com/products/762...rging_Relay_with_Manual_Control_-_12V_DC_500A This beast is rated to pass 500A, just what you want with a modern Ford or RAM with a 400A alternator setup.

I actually built my system with a Magnum SBC: http://magnumenergy.com/smart-battery-combiner-me-sbc/ coupled with a Blue Sea solenoid. I went with the Magnum because I though I needed a 15v cut out. In the end, I don't think I do. The Magnum does allow you to set the disconnect voltage to 12.5v. Higher than the Traxide, but lower than the Blue Sea.

Final points:

-- All of this assumes a modern truck running at between 14 and 14.5v at 70F. If your alternator does not run this high, you will have to raise the voltage or look at other products.

-- I tend to like Australian products as they really do have serious dirt roads. Is the Traxide for sale in the U.S., or would you be doing a one of importation? You might find the Blue Sea to be much less expensive.

-- I agree completely with the benefits of bidirectional charging.

-- Those who wish to really geek out on this can start reading here: http://www.smartgauge.co.uk/technical1.html :Wow1:

 

[expedition4x4]

I used a Bluesea Ml7622 which is much like the traxide but higher ratings

 

[007]

Diplostrat - very good points on the bigger systems, I'm a tacoma guy, so I appreciate the perspective on the bigger rigs.

 

[007]

I used a Bluesea Ml7622 which is much like the traxide but higher ratings

I thought that system automatically isolated the batteries after charging stopped. It has a manual combine option, but the traxide keeps the bateries combined untill significant drain and then it isolates to preserve enough power for starting. That blue sea system actually looks like it works more like a national luna style, but with an additional manual switch.

 

[expedition4x4]

I thought that system automatically isolated the batteries after charging stopped. It has a manual combine option, but the traxide keeps the bateries combined untill significant drain and then it isolates to preserve enough power for starting. That blue sea system actually looks like it works more like a national luna style, but with an additional manual switch.

From the instruction manual
ML-Series ACR Function

Automatically combines battery
banks when sensed voltage
levels are:
Above 13.5V for 30 sec.
Above 13.0V for 90 sec.


Automatically isolates battery
banks when sensed voltage
levels are:
Below 9.6V (undervoltage lockout)
Below 12.35V for 10 sec.
Below 12.75V for 30 sec.

I just finished install this afternoon so I have some more multimeter testing to do but this is how mine seems to be working

 

[wrcsixeight]

I like the idea of using some capacity from the engine battery, as long as it is not just a " starting" battery, and is a deep cycle or at least a Marine battery.

I used to have 3 group 27 batteries, two for the house and one for the engine. The engine battery never saw anything but engine starting Duties. After a while I started thinking about it as a 54 pound paperweight.

Now I've deliberately lowered my overall battery capacity. One 90 A/h AGM, and one 130 AH group 31 flooded. I can and do use either for house or engine starting duties. I've been keeping the AGM for mostly engine starting, but I am not afraid to discharge it. I once discharged 70 amp hours from it, and started my 5.2 liter V8 easily with that battery alone.

While I've lowered my overall available capacity, I now will use the engine battery to assist house loads if need be, where before I just always left it fully charged.
But I use manual switches, and have a battery monitor, and know how much I am using.

I also know if that I were to drain both batteries, that my 200 watts of solar would allow me to start the engine after half a day of sun, or less, but in my nightly cycling, this time of the year, I need to try and be wasteful to enter any dangerous territory, as far as battery state of charge.

 

[expedition4x4]

Confirmed the blue sea uses voltage sensed to Isolate, when it detects 12.75 or below it isolates the batteries when on the auto setting.

 

[Joe917]

Please correct me if I'm wrong but using a vehicles alternator to charge two batteries at different states of discharge is not efficient. Using a solenoid to protect the starting battery from accidental discharge is a good idea but for charging you are far better off with a battery to battery charger. Vehicle alternators are set up to quickly recharge a quickly discharged starting battery then drop to a float charge. Charging two batteries from a single regulated source will always undercharge one battery and overcharge the other.
http://www.sterling-power.com/products-battbatt-info.htm

 

[007]

Please correct me if I'm wrong but using a vehicles alternator to charge two batteries at different states of discharge is not efficient. Using a solenoid to protect the starting battery from accidental discharge is a good idea but for charging you are far better off with a battery to battery charger. Vehicle alternators are set up to quickly recharge a quickly discharged starting battery then drop to a float charge. Charging two batteries from a single regulated source will always undercharge one battery and overcharge the other.
http://www.sterling-power.com/products-battbatt-info.htm

I understand the dc to dc theory (increases charge voltage), but I think that comes at a price. To increase voltage, you lose amps, so bulk charging suffers. I would rather keep my bulk charge ability, and worry aboat float charging when I have shore power. Im a weekend/two week warrior with a two battery system YMMV.

 

[Joe917]

I understand the dc to dc theory (increases charge voltage), but I think that comes at a price. To increase voltage, you lose amps, so bulk charging suffers. I would rather keep my bulk charge ability, and worry aboat float charging when I have shore power. Im a weekend/two week warrior with a two battery system YMMV.

A DC to DC charger is not a float charger.
After start up it allows the alternator to recharge the starting battery. After full charge is reached (very quickly for a starter) it then starts to charge the house battery through the starter battery. The starting battery is kept at full charge and a proper four stage program brings the house up as efficiently as possible. Both batteries are charged as fast as possible and in a method which will give longest battery life. The catch is it is significantly more expensive than a solenoid. Check out the Stirling site(no affiliation).
I am not an electrician but am going through a motorhome rewire right now.
Cheers.

 

[DiploStrat]

Amps vs. Volts

Joe,

A battery to battery (B2B) does indeed trade amps to get volts, one reason that the largest that I have found, made by Sterling, is only rated to about 50A. These beasts work well:

-- If you only need 50A or less, and,
-- Your alternator only puts out 13 volts or so. (typical of an older vehicle)

In this case, 50A, delivered at a full 14.4v or which ever profile you select, and sensed at the camper battery, not the starter battery, will give you a much, much faster charge.

If you are working on an older motorhome, that runs at under 14v, then you would be better served with a Sterling Alternator to Battery charger (A2B). there are models that can handle up to 400A from the alternator. The only caveats on these are:

-- They are less necessary if you have a modern vehicle that runs at over 14v.
-- They have a hard shutdown at 15.5v input. (This cannot be reprogrammed.)
-- They are large and produce a lot of heat (due to the use of a diode).
-- They do not do bidirectional charging. (But there are ways to compensate for this.)
-- They are not cheap, but Defender Marine has better prices: http://www.defender.com/product3.jsp?path=-1|328|2289948|2289953&id=2086384

I tested one and achieved some exceptional charge rates.

 

[007]

My alternator is 130 amp, and the ctek dual 250 dc to dc charger is rated at 20 amp output.

I understand the ctek would bump my recharge voltage from 14.4 to 14.7, which is right where my deep cycle marine battery is supposed to be for optimal charge.

So the ctek charges at the most ideal voltage, but if it's only pumping out 20 amps, isn't this going to cause a much longer recharge rate? How long would it take to recharge two group 31 batteries at 50% discharge compared to the straight alternator?

If I understand this correctly, the dc to dc charger gives a more complete charge, but would take longer to do it, is that correct?

 

[DiploStrat]

Save Money!

If your truck has a 130A alternator producing 14.4v @ 70F, then you are pretty much there.

-- Wire it up with a cable of about 100mm2.
-- Control it with a smart relay rated at 150A or more, continuous. (The Traxide looks interesting if you can get a good price, else use one of the Blue Sea units.)
-- Spend the difference on a solar kit, say Blue Sky or Morning Star, rated at at least 100w.

If you are really concerned, there are products that you can use to tweak your alternator output 0.5v or so, but I wouldn't worry; I would just be sure that my solar kit or shore power unit had the most exact profile match.

So to answer your question, 75-100A @ 14.4v will probably charge a lot faster than 20A @ 14.7v.

This is what I installed on my truck to replace a Sterling A2B. As noted, I routine see around 150A @ 14.4v or higher, if it is cold. (The Chevrolet has a temperature sense on the starter batteries.)

Good luck!

Usual caveats: This is what I did/would do. It may or may not be the best answer for you. Etc.

 

[007]

Diplostat - Thanks for your help!

The Traxide system may be difficult to get my hands on in the states. A quick search found an adjustable solid state isolator: http://www.intervolt.com/products/electronic-battery-isolator/ebi-series.aspx

I like the idea that I could adjust the isolate voltage, but I don't think it has a provision for a cab mounted switch for combining the batteries on the fly.

Anyone using an adjustable Isolator?