Battery to battery chargers

[Robbie260]

Im putting a pure sine wave inverter and auxiliary battery in the bed of my new to me pickup. Will need to charge the battery have 2 auxiliary batteries i had bought for another project but never got around too lying in the shed think i can get away with one as they are both 110ah and it will only be running a few battery chargers and some power tools through a 1500w inverter posibly some lights etc. I have seen the red arc battery to battery chargers advertised but was wondering if there is any alternatives. Had found these as well and i like that it comes with all the bits so i dont have to worry about finding extras.

https://www.simplysplitcharge.co.uk/index.php?route=product/product&path=80_148_265&product_id=1077

 

[hotponyshoes]

Looks complicated and expensive to me (for what you need)
A regular smart charge relay (voltage sensing relay) should do the job
I have fitted a few of them and it's the relay itself, some cables and basic hardware like crimp terminals, fuse holders etc.
Cargo or Durite are decent quality.
If both of your aux battries are the same then just wire them up in parallel to double the capacity.

The downside is you wont be able to run the engine to use the inverter if the aux battries go flat (you would want an extra solonide for that(
The upside is you will still be able to start the car when they have gone flat.

The more power available for the inverter the better as most of them have a 'engine start protection' cut off so you can only actually use about 10% of the aux battries capacity.

 

[hotponyshoes]

If you don't want to shop around for all the bits let me know the lengths of the cable runs and I probably have enough stuff here to put a kit together for you

 

[hotponyshoes]

Also, you want to charge at about 10% of capacity so if you added both 110a batteries charge at 22a so a 30a kit would be fine and cheaper than a 50a

 

[Robbie260]

Looks complicated and expensive to me (for what you need)
A regular smart charge relay (voltage sensing relay) should do the job
I have fitted a few of them and it's the relay itself, some cables and basic hardware like crimp terminals, fuse holders etc.
Cargo or Durite are decent quality.
If both of your aux battries are the same then just wire them up in parallel to double the capacity.

The downside is you wont be able to run the engine to use the inverter if the aux battries go flat (you would want an extra solonide for that(
The upside is you will still be able to start the car when they have gone flat.

The more power available for the inverter the better as most of them have a 'engine start protection' cut off so you can only actually use about 10% of the aux battries capacity.

Ah good that a durite will probably do the job as i was looking at them the only thing was thinking that the ablity to charge from a solar panel may be handy i took it camping but could always add a mppt later.

I did not know about that with inverters ah thats a pain as they are two quite big auxilliary batterys.

If you don't want to shop around for all the bits let me know the lengths of the cable runs and I probably have enough stuff here to put a kit together for you

Thanks for the offer i may just take you up on that if i need to.

 

[Ashley Burton]

I've got a Ring RSCDC30 & very pleased with it

 

[hotponyshoes]

It depends on the inverter so read the spec sheet and see if it mentions engine start protection or low voltage cut-off or something like that.

To add smaller solar panel just connect it directly to the van battery then once that is fully charged the durite will click in and start charging the aux as well.
If you want to add a whole solar array get a bias charge controller (£40?) That will let you connect all the batteries and let you choose which order to charge them up in.

 

[hotponyshoes]

The ring unit and those sort are proper smart units, they can charge the aux battries at varying rates depending in how flat it is.
If you have the type of inverter with a cut out you wont get any benefits from one though and if you are mainly charging the aux battries when driving then the electronics in the cars alternator are going to do that job anyway.

Only times I have fitted things like that are to horse boxes when I want to charge 12v batteries for the living from the 24v lorry system.

 

[armalites]

The CTEK DC-DC chargers are supposed to be really good. From the stuff I've read they do a better job than a standard split charge relay

https://www.ctek.com/products?category=c106b614-7073-45ec-bd69-1a0dfeb6114e

 

[julianf]

The CTEK DC-DC chargers are supposed to be really good. From the stuff I've read they do a better job than a standard split charge relay

https://www.amazon.co.uk/CTEK-D250S...ocphy=9045425&hvtargid=pla-751143508532&psc=1

https://www.rotronicsbms.com/produc...t9qiqQ8ClSg-l6CaK_uhPLygwq0rnPBUaAuRVEALw_wcB

I have one of those ctek ones here - ive never installed it!

Why? Because the open circuit voltage restriction is stupidly low. And there are reports of people frying them by ignoring the spec.

With all the cheap 48v panels about, it works out cheaper to get a more sensible MPPT unit, and ditch the ctek.

 

[Robbie260]

Right so the inverter i have ordered dose have low input voltage protection. Its a 1500w inverter with a 3000w peak so i think it will be good for most average power tools.

 

[carbon]

I have one of the Ctek dc to dc chargers in my van to charge an agm battery has been there possibly two years without issue.

 

[Kayos]

I used a split charge but also a 3 way isolator so I could effectively connect the inverter to either or both batteries, depending what I was doing

 

[Ashley Burton]

@hotponyshoes it's a great unit!

I can also connect my solar panel up with it. It might not be cheaper than a split charge relay setup. But my thoughts is why spend good money on an aux battery to not look after it!

 

[m_c]

What van have you got?

DC to DC is the best option if you've got something new enough to have smart charging. You can get basic voltage sensitive split charge relays which have had the voltages adjusted to work with the varying voltage of smart charging, but there are still conditions where they will/won't connect when you don't/do want it to connect, and not charge the auxiliary batteries as quick as they could be.
If you do have something with smart charging, be aware of where you take the feed from. Take it from the wrong place (i.e. the wrong side of the battery current sensor), and it'll upset the smart charging and battery management system. All manufacturers should have a Body Builder Manuals/Vehicle conversion manual available that will detail recommended connection points.

For something non-smart charging, a basic voltage sensitive relay is likely to work well enough.

 

[hotponyshoes]

@hotponyshoes it's a great unit!

I can also connect my solar panel up with it. It might not be cheaper than a split charge relay setup. But my thoughts is why spend good money on an aux battery to not look after it!

I have fitted a couple before and they are pretty neat!
Probably overkill for the op though.
His inverter has a low voltage cut-off. That's not actually that low voltage, it will cut off around 11.5v so you can still start the car afterwards.
Obviously a downside for him as he is running a second battery(s) so does not need this protection and it will reduce the run time he can get out of it.
The inverter wont let the battery get low enough for the staged charging levels of the ring type chargers to kick in anyway. They will just go directly into the final top-off charge state and charge at the second slowest rate (final rate being the maintenance charge once fully charged)
If he's running power tools then he's going to need a pretty big array of solar power to make a dent on replacing the power used for that to be of any benefit.

Depends on how he is planning on using it but if it's for charging up and running tools on site then charging the inverter aux battries up when driving between jobs a faster charge would be better.
It will come at the expense of battery life span but use the batteries you have then once they die buy whatever is on offer at euro car parts at the time with a 5yr warranty and keep the receipt.

Right so the inverter i have ordered dose have low input voltage protection. Its a 1500w inverter with a 3000w peak so i think it will be good for most average power tools.

It will run most power tools rated up to 1500w.
Forget about the 3000w rating as that's sure for short periods only, ie on start up.
That's about 6a of output. Most chargers for cordless tools with 3-4ah batteries are only pulling a couple of amps so you could run 2 or 3 of those at once. The ratings will be on a sticker on the charger somewhere.
Some of the bigger stuff might be an issue, the latest bosch charger to charge the 12ah packs in 40mins is drawing 5.5a or so.
Having said that, all of my own trucks have had inverters and aux batteries fitted except the last one I did a year or so ago. I figured 12ah battries in the drill/grinder/etc are going to last me all day anyway.
The van is newer with fancy electronics so the led work lights etc I was able to connect to a body builder plug that's monitored so I dont need to worry about draining the battery and not being able to start the van.

 

[Robbie260]

What van have you got?

DC to DC is the best option if you've got something new enough to have smart charging. You can get basic voltage sensitive split charge relays which have had the voltages adjusted to work with the varying voltage of smart charging, but there are still conditions where they will/won't connect when you don't/do want it to connect, and not charge the auxiliary batteries as quick as they could be.
If you do have something with smart charging, be aware of where you take the feed from. Take it from the wrong place (i.e. the wrong side of the battery current sensor), and it'll upset the smart charging and battery management system. All manufacturers should have a Body Builder Manuals/Vehicle conversion manual available that will detail recommended connection points.

For something non-smart charging, a basic voltage sensitive relay is likely to work well enough.

Its a 2016 isuzu dmax 2.5 twin turbo.

I have fitted a couple before and they are pretty neat!
Probably overkill for the op though.
His inverter has a low voltage cut-off. That's not actually that low voltage, it will cut off around 11.5v so you can still start the car afterwards.
Obviously a downside for him as he is running a second battery(s) so does not need this protection and it will reduce the run time he can get out of it.
The inverter wont let the battery get low enough for the staged charging levels of the ring type chargers to kick in anyway. They will just go directly into the final top-off charge state and charge at the second slowest rate (final rate being the maintenance charge once fully charged)
If he's running power tools then he's going to need a pretty big array of solar power to make a dent on replacing the power used for that to be of any benefit.

Depends on how he is planning on using it but if it's for charging up and running tools on site then charging the inverter aux battries up when driving between jobs a faster charge would be better.
It will come at the expense of battery life span but use the batteries you have then once they die buy whatever is on offer at euro car parts at the time with a 5yr warranty and keep the receipt.



It will run most power tools rated up to 1500w.
Forget about the 3000w rating as that's sure for short periods only, ie on start up.
That's about 6a of output. Most chargers for cordless tools with 3-4ah batteries are only pulling a couple of amps so you could run 2 or 3 of those at once. The ratings will be on a sticker on the charger somewhere.
Some of the bigger stuff might be an issue, the latest bosch charger to charge the 12ah packs in 40mins is drawing 5.5a or so.
Having said that, all of my own trucks have had inverters and aux batteries fitted except the last one I did a year or so ago. I figured 12ah battries in the drill/grinder/etc are going to last me all day anyway.
The van is newer with fancy electronics so the led work lights etc I was able to connect to a body builder plug that's monitored so I dont need to worry about draining the battery and not being able to start the van.

Yeah the solar pannel was only for possible camping but there should be more than enough capacity there to last me for an overnight stop if im driving on the next day. Seems like the voltage sensing relay is the best bet will go with one of them as the pockets a little light at the moment. Any one know the best place to get these durite relays from.

 

[hotponyshoes]

Pop the bonnet and check what type of battery you have fitted, if it's a standard lead acid then you are good to go.

You want to find a local auto-electrical place then you can go in and buy the right amount of cable and fuse holders etc. You can also buy the terminals individually rather than having to buy packs of 10 or pay postage for each one.

Otherwise, somewhere like vehiclewiringproducts.co.uk

 

[Ashley Burton]

I would say get a generator or buy cordless tools where suits. Using an inverter isn't the way I would be looking to run power tools personally

 

[Robbie260]

I would say get a generator or buy cordless tools where suits. Using an inverter isn't the way I would be looking to run power tools personally

I have bought cordless so it will be charging batteries for the most part only metal and wood working circular saws and 7 inch angle grinder and die grinder and very occasionally a miter or chop saw to run off the 240v properly. I have even gotten a cordless battery welder to do the jobs i want a lorch micor tig 200 basic with battery and i will review that all for you later ounce i get it all sorted and had a chance to play wont be untill next week unfortunately.

Dont want a generator if i can avoid it as some places i want to work i cannot make that much noise and i am a mechanical/electrical engineer and i dont want yet another piece of equipment to maintain if i dont have too.