What to do when your vehicle has a factory dual battery ?

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tchamberlin

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I recently got this Toyota HDJ100 ( 1HDFTE engine) with factory dual batteries. I have been told this is manly done because its good to have the extra cranking amp for the diesel and more storage because its Africa. The batteries are linked and matched. I want to be able to run accessories and fridge at some point. The question is should I convert one battery to an accessory battery with DC-DC system or should i keep the two as is and add a 3rd? I have some room where i can put it i think, thought it might be a bit small. My concern converting one to an accessory battery will reduce my available cranking amps. Adding a 3rd battery also seems like it would be easier?
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oldmopars

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Because you really only need the second battery during cranking, you may be able use a relay to have both batteries connected during starting and running, but have them disconnected while the rig is off. This way they will be there for engine cranking, they will both get charged, but when it is not running you only pull current from one battery.
This may not be a perfect system because the "House" battery will get drained down and then when you go to start the batteries will not be balanced. However, if you keep the demand low, it should be OK. A 3rd battery would be good, but the down side is the extra weight and complexity of adding more wiring. And space.
My suggestion would be to go with the first option and get the best Lithium batteries you can find to fit the application. They will give better performance and they allow you to drain them deeper before things quit working. They are also less than half the weight.
If you are always on the move never staying in one place more than a night, solar is not a great option. However if you are going to stay in one place for several days, solar will keep the battery up during the days while you are not driving.
If you are on the move all the time, your batteries are being used at night, when there is no sun and recharged during the day when you are driving and the engine is charging. Solar would not help.
 

MidOH

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I'd go with a 3rd battery. House only. You can even use a little g26 to save weight.
 
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Dilldog

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Its hard to tell if you have any room to go to a bigger battery or not from the picture, but thats what I would look into (those look like group 34s, upgrade one to a 31 and keep the other the same). Run one large battery for starting, then in the second location isolate it with an automatic set up for other stuff. Not knowing much about that engine I cant say too much, I know it being a smaller electronic diesel you wouldnt want to run any less than 700CCA, but if it has an electric pre heater for cold starts you probably would want to stay up around 900CCA to be safe.
 

Boostpowered

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My small 4cyl colorado diesel runs a large single 1000cca battery for starting. I would guess you need both of those smaller batteries to get the cranking amps you need. My 2cyl diesel yanmar tractor uses a single 660cca just to get an idea the bigger the diesel the more amps needed to start it. Actually i can see that you need both since they are wired in series - to+ to - to+ instead of parallel -to- and +to+
 
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Dilldog

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My small 4cyl colorado diesel runs a large single 1000cca battery for starting. I would guess you need both of those smaller batteries to get the cranking amps you need. My 2cyl diesel yanmar tractor uses a single 660cca just to get an idea the bigger the diesel the more amps needed to start it. Actually i can see that you need both since they are wired in series - to+ to - to+ instead of parallel -to- and +to+
Wow missed that series wiring thing. That would mean your electrical system (at least for starting) is 24 volt. No way to avoid two batteries. In addition if your alternator is a 24 volt unit you won't be able to just add one battery and have your alternator work to charge it. Before going any further you will want to check and see if the whole rig is 24 volt.
 

M Rose

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They make a 24 to 12 volt converter.... the us army uses them on the LMTV trucks to go from 24 volt cranking to 12 v inside the cab and for the led lights. your truck probably already has this device and its a great place to tie in an auxiliary fuse and relay block.
 

shoredreamer

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Congrats on the HDJ100. We can all dream here in the states. Diesel Toyotas have 24v starting so you’d want to add a 3rd battery in the cargo area. Mount a DCtoDC charger near the 3rd battery, wire it up and you’re set!
 
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tchamberlin

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Congrats on the HDJ100. We can all dream here in the states. Diesel Toyotas have 24v starting so you’d want to add a 3rd battery in the cargo area. Mount a DCtoDC charger near the 3rd battery, wire it up and you’re set!
Thanks, that makes a lot of sense. I like the idea of a removable accessory system too.