![]() | Home > Maintenance & Mods (L322) > An upgraded dual battery idea. |
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kingpleb Member Since: 07 Jun 2011 Location: Maybe here. Maybe there, I get everywhere! Posts: 8455 ![]() ![]() ![]() |
I think if you put a battery as per Dans method you will be fine with venting.
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barracuda816 Member Since: 11 Jun 2012 Location: oxfordshire Posts: 213 ![]() ![]() ![]() |
venting wouldn't be too much of a hassle with most "sealed" batteries, many have a vent plug on the top which you can route a little pipe upto the vent that is about 3" higher.
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barracuda816 Member Since: 11 Jun 2012 Location: oxfordshire Posts: 213 ![]() ![]() ![]() |
The main three problems i see with Dans system are:
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mzplcg Member Since: 26 May 2010 Location: Warwickshire. England. The Commonwealth. Posts: 4029 ![]() ![]() ![]() |
OK, I'll take your points one at a time.
That is only going to happen over several months. Your assumption that it will all be in one direction is wrong. What actually happens is that the weaker of the two batteries will draw from the stronger until the voltage in the stronger becomes lower than the voltage in the weaker. At this point the current flow will reverse. Now, this process is like watching a see-saw in slow motion. Internal resistance in batteries is very low so the to and fro action is miniscule.
Nope. Sorry, the amount of charge a battery will accept has nothing to do with alternator output. A battery is almost impossible to overcharge unless you hike up the voltage output of the charging source. VOLTAGE, not current. You need a PD between supply and load in order for current to flow.
Probably true, but to run down 2 batteries with AGM technology will be a fairly impressive feat. As I said before, if you manage to flatten 165 ah of Gel technology you either need to get some alzheimers tablets and stop forgetting what you've left on, or you need a bigger car. Perhaps consider one of those Alde trailers with a load of batteries in. ![]() |
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nicedayforit Member Since: 11 Jun 2011 Location: Beside the Solway Posts: 3977 ![]() ![]() ![]() |
@barracuda816
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barracuda816 Member Since: 11 Jun 2012 Location: oxfordshire Posts: 213 ![]() ![]() ![]() |
![]() I take your point on issue one, as long as both are the same type it should be minimal, and as it will be driven almost daily its a non issue i suppose. I didnt know they would effectively see-saw though it makes sense when you look at it. point 2, i Dont know why i thought that, (i do know it wouldnt overcharge at 14.2ish, honest ![]() Point 3, I agree under normal use, 160ah would probably be sufficient. But for even weekend camping it would be easy to run them below 50% dod. The main thing with my idea is i "should" never be unable to start the engine. I will probably run the simple parallel set up due to cost, but when i have the readies i may try the below set up (again please excuse the poor diagram, its just to give an overview) With the disengaging/engaging of the batteries do you think it would suffer from transient voltage spikes? ![]() Uploaded with ImageShack.us Plus with this it would be extreamly easy to add further dedicated batteries (a winch batt ect) |
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barracuda816 Member Since: 11 Jun 2012 Location: oxfordshire Posts: 213 ![]() ![]() ![]() |
@ nicedayforit
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nicedayforit Member Since: 11 Jun 2011 Location: Beside the Solway Posts: 3977 ![]() ![]() ![]() |
"I understand what you are saying, but if i where to add a second battery the standard relay way, the main (starter battery) would still be connected to all the on board computers, RSE , FBH ect. And the 8awg wire running to the second battery will not be anywhere near man enough to carry the required current to start the engine."
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wats39 Member Since: 08 Jul 2012 Location: fife Posts: 77 ![]() ![]() ![]() |
Nicedayforit, i think Barracuda is talking about disconnecting the earth cable from the main battery to isolate it therefore he will need a high capacity relay to take the current draw from the starter motor. the way you are suggesting is the same as me i think. using a smaller relay to disconnect the + on both batteries when the ignition is off. the relay is only used for charging then and not starting. i am pretty sure there are just two + cables at the main battery, one for the starter and the other for supplying everything else. now all you would have to do is put the relay between the main battery + terminal and this cable for supplying everything else and have it switched with your ignition. this would then isloate the main/starter battery from the rear one with the ignition off and join them for charging with the ignition on. Barracuda, the way you are suggesting will work but i think this way is by far the cheapest and the end result will be the same. also for a rear battery you would prob be better using a deep cycle battery as these are designed to be discharged and recharged a lot where as the starter batteries are not and wont last very long. '04 td6 se
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barracuda816 Member Since: 11 Jun 2012 Location: oxfordshire Posts: 213 ![]() ![]() ![]() |
wats39,
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nicedayforit Member Since: 11 Jun 2011 Location: Beside the Solway Posts: 3977 ![]() ![]() ![]() |
Send me your email address by pm Luke and I will send you the vehicle wiring diagrams. |
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wats39 Member Since: 08 Jul 2012 Location: fife Posts: 77 ![]() ![]() ![]() |
Barracuda, will try get time tomorrow and have a look at mine to see if there is just the 2 wires that i think there is. a wiring diagram would be ideal but you dont seem to get them for any vehicles these days. prob to do with the amount of wiring in them now |
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wats39 Member Since: 08 Jul 2012 Location: fife Posts: 77 ![]() ![]() ![]() |
I stand corrected. where did you get the wiring diagrams from Nicedayforit? '04 td6 se
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nicedayforit Member Since: 11 Jun 2011 Location: Beside the Solway Posts: 3977 ![]() ![]() ![]() |
Can't remember but if you pm me your email you are quite welcome to a copy.
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