Split Charge

StreetSleeper

StreetSleeper

Forum Member
I have decided to move away from motorhomes at this present time and go back to motorbiking; well not quite. This time I am using a trike and, for sleeping arrangements, we will be using a 1970 portafold folding caravan. The portafold needs a lot of work to bring it back to it's former glory but it's all doable, just needs time and money. At the momen, I am trying to wire up another battery that will sit in the boot of the trike, I have chosen a lithium golf trolly battery as my second battery as it's a nice size and it can't leak . So my question is, how will I charge the second battery? Here we have the two batteries
1656431742917.png

The leisure battery ................................................................................................................................. The main battery
1656431814025.png
 
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Pudsey Bear

Pudsey Bear

Forum Member
Get a VSR, voltage sensing relay, pick up on the positive lead from the trike battery, take another to the trailer battery and one to earth, the relay senses the trike is being charged & then opens the large contact in the relay and sends power to the trailer, when the engine is turned off the connection is broken, unless you are running a fridge you might even get away with a spotlight relay, it all depends on the loads, I'll shut up now as Mr Bus might (probably) have a better idea, but that's how I did my self build, and actually how I got around a buggered PCB (£650 to repair) on this van.

this video explains it I think.

 
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mistericeman

mistericeman

Forum Member
Pudsey Bear said:
Get a VSR, voltage sensing relay, pick up on the positive lead from the trike battery, take another to the trailer battery and one to earth, the relay senses the trike is being charged & then opens the large contact in the relay and sends power to the trailer, when the engine is turned off the connection is broken, unless you are running a fridge you might even get away with a spotlight relay, it all depends on the loads, I'll shut up now as Mr Bus might (probably) have a better idea, but that's how I did my self build, and actually how I got around a buggered PCB (£650 to repair) on this van.

this video explains it I think.

Click to expand...

Didn't think a VSR would correctly charge a lithium battery?
 
StreetSleeper

StreetSleeper

Forum Member
As you can see, here's where I hope to house the battery, split charger, inverter and solar charger: short cable run on the 12 volt and a longer run on the 240
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wildebus

Forum Member
I think I would go for the following:
Victron Orion-Tr Smart DC-DC (B2B) Charger 18A Isolated - This will give you a charge level more than suitable for that size battery and also ensure the charge voltage is not in excess of what a Lithium Battery wants (I don't know how regulated a bike alternator is and a basic relay just passes through the voltage level); Isolated is good as well as it seperates the leisure electrics entirely from the trike except via the B2B.
10mm2 cable from the battery to B2B In; then output to an 50A Anderson Connector, and then the Anderson connector with 10mm2 cables to the Battery. Using Andersons means it would be very easy to use an extension from boot to popup if you happened to have a battery in the trailer and you wanted to charge that - just a quick change of plug leads. In Oz they are well into using Andersons between their Utes and off-road trailers as much more reliable and capable then basic towing connectors.
Cost-wise, the above could be done for under £150.

What size of Inverter are you looking at here? With that size of lithium battery you will be pretty limited in the maximum current you can draw (maybe no more than 300W load could be a maximum).
 
Squiffy

Squiffy

Forum Member
StreetSleeper said:
I have decided to move away from motorhomes at this present time and go back to motorbiking; well not quite. This time I am using a trike and, for sleeping arrangements, we will be using a 1970 portafold folding caravan. The portafold needs a lot of work to bring it back to it's former glory but it's all doable, just needs time and money. At the momen, I am trying to wire up another battery that will sit in the boot of the trike, I have chosen a lithium golf trolly battery as my second battery as it's a nice size and it can't leak . So my question is, how will I charge the second battery? Here we have the two batteriesView attachment 5415
The leisure battery ................................................................................................................................. The main batteryView attachment 5416
Click to expand...
This could be of interest StreetSleeper. Phil

https://www.fastbikegear.co.nz/inde...n inbuilt BMS you,with an external BMS system.
 
StreetSleeper

StreetSleeper

Forum Member
wildebus said:
that size of lithium battery you will be pretty limited in the maximum current you can draw (maybe no more than 300W load could be a maximum).
Click to expand...
That's a shame, my maths must have been out, I wanted to use a 400w Remoska. Still not to worry I've still got my petrol stove or the two ring gas cooker. All my other appliances should run quite happily off a 300w inverter.
 

wildebus

Forum Member
StreetSleeper said:
That's a shame, my maths must have been out, I wanted to use a 400w Remoska. Still not to worry I've still got my petrol stove or the two ring gas cooker. All my other appliances should run quite happily off a 300w inverter.
Click to expand...
It is down to the size of the battery. You generally cannot (and would not really want to) take more than a C1 discharge out a lithium battery.
C1 means 1A for each 1Ah of capacity. That battery you have got is a 22Ah unit and it supports a 25A continuous discharge (so a little higher than C1 in fact). 25A@13V (which is pushing it. Voltage at that discharge probably lower) means 325W out the battery. With inverter losses of say 15-20%, you are actually looking at an maximum actual Inverter output of maybe 275W peak :(
 

Derekoak

Forum Member
StreetSleeper said:
I have decided to move away from motorhomes at this present time and go back to motorbiking; well not quite. This time I am using a trike and, for sleeping arrangements, we will be using a 1970 portafold folding caravan. The portafold needs a lot of work to bring it back to it's former glory but it's all doable, just needs time and money. At the momen, I am trying to wire up another battery that will sit in the boot of the trike, I have chosen a lithium golf trolly battery as my second battery as it's a nice size and it can't leak . So my question is, how will I charge the second battery? Here we have the two batteriesView attachment 5415
The leisure battery ................................................................................................................................. The main batteryView attachment 5416
Click to expand...
The trouble with a vsr for lithium is the voltages are for lead and are wrong for lithium. A victron li ct is a vsr with the right voltages for lithium, it cost 80 pounds ish. If you are on a budget a manual switch from ignition live to a relay large enough to take the charge load is the cheapest way to charge lithium from your engine.
You do need to think about when to switch, but if you forget to switch off, with engine off the 2 batteries are only connected if you leave the ignition on. I find that unlikely.
You would need to check that the cable was the right size to not deliver too much charge to overload your alternator or battery. For example I have 120 amp alternator 200 ah lithium and 3.5m long 16mm cable that gives 60 amp maximum charge rate, which is safe for both battery and alternator.
 
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wildebus

Forum Member
Derekoak said:
The trouble with a vsr for lithium is the voltages are for lead and are wrong for lithium. A victron li ct is a vsr with the right voltages for lithium, it cost 80 pounds ish. If you are on a budget a manual switch from ignition live to a relay large enough to take the charge load is the cheapest way to charge lithium from your engine.
You do need to think about when to switch, but if you forget to switch off, with engine off the 2 batteries are only connected if you leave the ignition on. I find that unlikely.
Click to expand...
Just a comment on the Li-ct.
I know the Victron Li-ct seems to be the relay of choice when it comes to a simple split-charge setup for Lithium, but I am not sure it is automatically really the right choice. It is designed to be used with Lithium Batteries with external BMS systems where you can connect a control signal to the relay to disconnect it when the battery is full, or if the event of a fault condition.
With the great majority of Lithium Batteries that people buy, the BMS is internal and there is no communication possible from the battery to the relay - this means that the Cyrix-Li-ct will operate in exactly the same way as the Cyrix-ct would on a Lead battery i.e. Once engaged, it will stay engaged permenantly until the engine is turned off.
The only advantage it has over the Cyrix-ct and other VSRs is the disconnect voltage is suitable for Lithium ('normal' VSRs wil not disconnect with a Lithium system as their disconnect threshold is lower than a Lithium batteries normal resting voltage). It offers no advantage (other then likely better quality of manufacture) then a basic relay that is controlled by the D+ signal from the alternator, especially when used with such a small battery that will only take a low (in terms of typical Leisure Lithium Batteries) charge current.
A standard Automotive relay such as one of these - https://amzn.to/3QVw0UJ - is a far more cost-effective solution than a Cyrix-Li-ct, when a current capability of 120A is way over the top.
I know you mentioned the option of a switched relay, but I would not see this as the "on a budget" option over the Li-ct, but a more sensible option for this particular install considering it offers no downside over the Li-ct but can be obtained at around 1/20th of the price you quoted for the Li-ct.
 

Derekoak

Forum Member
My system does not overcharge the battery with either just switched or with the lict, because my bms is set to switch off at just below 14v. I can't see the problem with my system but perhaps the lict was surplus. I switch on manually after a few minutes running to be kind to the alternator and switch off manually when I think my lithium can be charged from my solar.
 
StreetSleeper

StreetSleeper

Forum Member
This is what i was going to use for the trike with an 800w streetwize inverter and i do know i cant use 800w on full power with my battery
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Nabsim

Nabsim

Forum Member
Rae, when I had problems with my EBL/control panel I didn’t expect it back in time to refit before going off again last winter. I bought a pack of 6 usb rechargeable puck lights that turn on/off by touch or remote, low and high settings and timers, stitch with double sided tape, screw or magnetic. Cost around £20.

If you are only after lights get something like that and recharge from trike usb or power bank 👍
 
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