Robthebrit
Explorer
there is a typo above:
for a 0.75amp load over 64 hours: 0.75^1.15 * 64 = 45.9 aH drain
Rob
for a 0.75amp load over 64 hours: 0.75^1.15 * 64 = 45.9 aH drain
Rob
fridge power consumption?
- Thread starter jeffryscott
- Start date
jeffryscott
2006 Rally Course Champion: Expedition Trophy
Thanks Rob,
That is good info and makes me think the Optima Yellow or Blue would work fine.
Now, I know I've seen this in earlier threads, but what is a good, inexpensive way to hook things up.
I will have the fridge, winch, IPF lights and accessories (CB, iPod, GPS and miscellaneous small electronics) to run. Obviously the fridge will be the big draw except when the winch is used.
Thanks again.
That is good info and makes me think the Optima Yellow or Blue would work fine.
Now, I know I've seen this in earlier threads, but what is a good, inexpensive way to hook things up.
I will have the fridge, winch, IPF lights and accessories (CB, iPod, GPS and miscellaneous small electronics) to run. Obviously the fridge will be the big draw except when the winch is used.
Thanks again.
Robthebrit
Explorer
An optima will work well for what you want. I'll tell you what I did with my setup, however, I am sure there are as many opinions as there are people on this forum.
I split the batteries with a xantrex split charge system and made 2 catogries of devices, catogory 1 is things that run while the truck is on such as the stock electrical components and the rally/spot lights, inside radio etc. These items run off the main battery as they are not likely to be on if the engine is off, if they are going to be on they are not on for long (a modern truck will have more items in the category than my old diesel). Category 2 items are things which run from the Aux battery when the truck is off such as Fridge, Camp lights, misc camp electronics. I also have 2 different colored 12v sockets inside and outside the truck, one color is for one battery and one for the other.
The winch is a special case as you probably want to parallel the batteries to give more winching time, you need to use the battery as no 12V alternator is powerful enough to drive a loaded winch. Most split chargers worth their money have a feature to join the batteries together but check the max power carefully. With this setup you do not want to winch with the engine off as you will flatten both batteries and be stuck.
Like I said this is just my take, I think its best to leave the truck/starting battery untouched and put all the load on the aux battery. Others like to put all the load on the truck battery and use the aux battery (via the join mode on the split charger) to start the truck. Both options are valid for different reasons, the reason I chose the method I did mainly because the cranking current to turn my engine over can be over 1000A on a cold day and no split charger is going to handle that. The nethod of starting from the aux battery is an additional point of failure because it requires the split charger to work. If the split charger breaks you cannot start the truck, however, this is probably not a realistic worry as you could physically swap the batteries or jump one from the other with regular jump leads.
Make a plan and run it past the forum, you'll get plenty of feedback as this has been done lots of times before. Most importantly do what suits you and the way you use your truck. If you want to contact me off list, feel free.
Rob
I split the batteries with a xantrex split charge system and made 2 catogries of devices, catogory 1 is things that run while the truck is on such as the stock electrical components and the rally/spot lights, inside radio etc. These items run off the main battery as they are not likely to be on if the engine is off, if they are going to be on they are not on for long (a modern truck will have more items in the category than my old diesel). Category 2 items are things which run from the Aux battery when the truck is off such as Fridge, Camp lights, misc camp electronics. I also have 2 different colored 12v sockets inside and outside the truck, one color is for one battery and one for the other.
The winch is a special case as you probably want to parallel the batteries to give more winching time, you need to use the battery as no 12V alternator is powerful enough to drive a loaded winch. Most split chargers worth their money have a feature to join the batteries together but check the max power carefully. With this setup you do not want to winch with the engine off as you will flatten both batteries and be stuck.
Like I said this is just my take, I think its best to leave the truck/starting battery untouched and put all the load on the aux battery. Others like to put all the load on the truck battery and use the aux battery (via the join mode on the split charger) to start the truck. Both options are valid for different reasons, the reason I chose the method I did mainly because the cranking current to turn my engine over can be over 1000A on a cold day and no split charger is going to handle that. The nethod of starting from the aux battery is an additional point of failure because it requires the split charger to work. If the split charger breaks you cannot start the truck, however, this is probably not a realistic worry as you could physically swap the batteries or jump one from the other with regular jump leads.
Make a plan and run it past the forum, you'll get plenty of feedback as this has been done lots of times before. Most importantly do what suits you and the way you use your truck. If you want to contact me off list, feel free.
Rob
Ursidae69
Traveller
Robthebrit said:
Great thread. :bowdown:
I was wondering if anyone has simply ran their fridge until it quits to see if the equations' results are close to reality? Is that bad for the fridge? Lastly, if you are at a remote camp for ten days, how long would you have to run the motor to get the aux battery back up to par for a few more days of fridge power?
Robthebrit
Explorer
The equation is fairly accurate and it is used alot in engineering. Its derived from solid principles although there is some simplifications as temperature and current state of the battery are not factored, in its true form the Peukert equation is quite nasty. The biggest error is going to come from obtaining the constant for a given battery as a slight change in those constants makes a huge difference to the result. You can compute the Peukert constant emperically by placing a constant load on a fully charged battery and timing how long it took to drop a certain voltage, after recharging to the same state do it again with a different load, repeat with many different loads for more accurate results. The amount of voltage you drop in the test is irrelevent, the time to drop a fixed voltage is what matters. You can go all the way to 10.5v but it takes a while but you do get more accurate results.
An Engel fridge has no disconnect and I cannot imagine it is good for it to run much below 10.5 volts. The ARBs and other versions of the same engel body do typically have disconnects. I think to test the theory you would need to keep going until you got to 10.5v.
For you folks that like gadgets and technology xantrex makes a power meter which which correctly measures drain based on load and estimates how many Ah are left in the battery. I made one myself a while back from a PIC chip that plugs into the serial port on a PC, the software would log drain and battery usage, draw graphs and calculate capacity remaining. I need to dig that out again...
Rob
An Engel fridge has no disconnect and I cannot imagine it is good for it to run much below 10.5 volts. The ARBs and other versions of the same engel body do typically have disconnects. I think to test the theory you would need to keep going until you got to 10.5v.
For you folks that like gadgets and technology xantrex makes a power meter which which correctly measures drain based on load and estimates how many Ah are left in the battery. I made one myself a while back from a PIC chip that plugs into the serial port on a PC, the software would log drain and battery usage, draw graphs and calculate capacity remaining. I need to dig that out again...
Rob
BajaTaco
Swashbuckler
Rob, this is fantastic info you are contributing. Thanks.
They have these on the EarthRoamers. Highly useful! ...and fun to watch in action.
Now that is cool
Jeff, one of the most simple/economical setups that I can think of for your app. would be to run the accessories off of the auxiliary battery, and use a SurePower isolator. A higher priced option would be to use the new MobiArc units which are super simple and very compact (a plus for your vehicle).
Robthebrit said:
They have these on the EarthRoamers. Highly useful! ...and fun to watch in action.
Robthebrit said:
Now that is cool
Jeff, one of the most simple/economical setups that I can think of for your app. would be to run the accessories off of the auxiliary battery, and use a SurePower isolator. A higher priced option would be to use the new MobiArc units which are super simple and very compact (a plus for your vehicle).
jeffryscott
2006 Rally Course Champion: Expedition Trophy
Chris, Rob, Baz and the others that helped walk me through this process, I bought a blue top at Costco yesterday - the dual purpose d34 (starting and deep cycle). For some reason, the blue top was $10 cheaper than the yellow top, yet they both have the same specs. I remember reading here there was no known difference between yellow and blue, so I went blue (the price difference paid for the trail mix my girls love).
I'll pick up the battery isolator at Checker tomorrow (the cheap one Baja Taco recommended, can't find prices on the super cool one).
Thanks, now to figure out where to mount the second battery and start getting things together.
(I'm thinking I should keep the Red Top as my starting battery, correct?)
Coool folks, thanks.
I'll pick up the battery isolator at Checker tomorrow (the cheap one Baja Taco recommended, can't find prices on the super cool one).
Thanks, now to figure out where to mount the second battery and start getting things together.
(I'm thinking I should keep the Red Top as my starting battery, correct?)
Coool folks, thanks.
jeffryscott
2006 Rally Course Champion: Expedition Trophy
Got it the fridge and blue top installed yesterday (see this thread for a pic: http://expeditionportal.com/forum/showthread.php?t=1491&page=3 ) and woke up this a.m. to a dead battery.
Since it is a deep cycle battery, what is the danger in running it down to where it won't start the car (alarm still worked, and the radio setting were still stored).
Also, what are the dangers of having the fridge running when the battery drops that low?
Two things I need to do: make a switch so I can turn the fridge on and off, and get the second battery setup up and running.
Thanks gang.
Since it is a deep cycle battery, what is the danger in running it down to where it won't start the car (alarm still worked, and the radio setting were still stored).
Also, what are the dangers of having the fridge running when the battery drops that low?
Two things I need to do: make a switch so I can turn the fridge on and off, and get the second battery setup up and running.
Thanks gang.
BajaTaco
Swashbuckler
Wow, that was fast! It's hard to know exactly what happened with the battery, and why it went flat. Since it is new, I wouldn't worry about any damage at this point. Just charge it back up. Did you charge it before you used it overnight? If it came off of a shelf at Costco and then didn't get fully charged before it was put to use running the fridge overnight, that may explain it. Also, have you been able to tell how much the fridge is running? I think doing a little "bench testing" of the fridge and battery would be a good idea. Maybe do it on a weekend so you can start running it in the morning, check the temps along the course of the day, and try to see if you can get some average run times. All the while checking the battery voltage.
BTW, I would agree on using the red top for your starting battery.
BTW, I would agree on using the red top for your starting battery.
Robthebrit
Explorer
Did you install the isolator or are you running everything from the bluetop? If you did install the isolator, how did you manage to flatten the starting battery?
I will second what BajaTaco said about the battery, a gentle discharge is not going to hurt a new battery and after a full recharge it will be as good as new. In fact it may be better than new as most lead acid batteries do not give their full capacity until theu have been discharged a few times. I would question the initial state of charge when you bought the battery. The battery should not go flat over night powering just a fridge. I have left my MT35 in the back of my dodge, in the LA Summer, plugged in to a none isolated outlet and had no problems starting after a weekend (Its a diesel so has two batteries but they are the factory rubbish batteries).
Fully charge the battery and hook up a volt meter so you can keep your eye on what is going on. Basically you want to see how long it takes to drop to 10.5 volts which is the point at which most battery disconnects switch off. You must measure the voltage while the fridge is running otherwise you'll measure the open voltage which will be near the expected 12.6V. The more current you draw from a discharged battery the lower the measured voltage will be, this is why your radio and lights continues to work (low current) but it will not start (high current).
A low voltage disconnect will protect your inverters, fridges and other equipment but will typically switch off too late to allow you to start. Most disconnects will warn you at around 10.5 volts and switch off at something like 10V. A battery in this state will more that likely not start an engine, definately not a diesel.
If the isolator is working you should not need to protect the starting battery.
Rob
I will second what BajaTaco said about the battery, a gentle discharge is not going to hurt a new battery and after a full recharge it will be as good as new. In fact it may be better than new as most lead acid batteries do not give their full capacity until theu have been discharged a few times. I would question the initial state of charge when you bought the battery. The battery should not go flat over night powering just a fridge. I have left my MT35 in the back of my dodge, in the LA Summer, plugged in to a none isolated outlet and had no problems starting after a weekend (Its a diesel so has two batteries but they are the factory rubbish batteries).
Fully charge the battery and hook up a volt meter so you can keep your eye on what is going on. Basically you want to see how long it takes to drop to 10.5 volts which is the point at which most battery disconnects switch off. You must measure the voltage while the fridge is running otherwise you'll measure the open voltage which will be near the expected 12.6V. The more current you draw from a discharged battery the lower the measured voltage will be, this is why your radio and lights continues to work (low current) but it will not start (high current).
A low voltage disconnect will protect your inverters, fridges and other equipment but will typically switch off too late to allow you to start. Most disconnects will warn you at around 10.5 volts and switch off at something like 10V. A battery in this state will more that likely not start an engine, definately not a diesel.
If the isolator is working you should not need to protect the starting battery.
Rob
jeffryscott
2006 Rally Course Champion: Expedition Trophy
Thanks again everybody, wouldn't have a clue about some of this without the advice here.
Running everything from the blue top at this point. Have the battery isolator in the back, in a bag.
I think part of the problem was the fridge hadn't cooled down at all and I installed the brand new battery, which probably was not fully charged, and then let it sit, didn't even drive it.
Since I've been driving it, all is well. I do need to get some diagnostic stuff done so I have a better idea of things, but, that will have to wait (I don't have any tools for that and have spent a wad getting this far).
Currently, everything is wired together with wire nuts. I need to install a fuse block so I can put the fridge, 12v plug and additional accessories (will install the CB on the block and when I get bare wire plugs and an external antenna for the GPS, will install it there as well.)
One step at a time ...
Running everything from the blue top at this point. Have the battery isolator in the back, in a bag.
I think part of the problem was the fridge hadn't cooled down at all and I installed the brand new battery, which probably was not fully charged, and then let it sit, didn't even drive it.
Since I've been driving it, all is well. I do need to get some diagnostic stuff done so I have a better idea of things, but, that will have to wait (I don't have any tools for that and have spent a wad getting this far).
Currently, everything is wired together with wire nuts. I need to install a fuse block so I can put the fridge, 12v plug and additional accessories (will install the CB on the block and when I get bare wire plugs and an external antenna for the GPS, will install it there as well.)
One step at a time ...