Battery Combiner with 300ah?

Pugwash69

Full Member
I was just reading the document by Wildebus about split charge relay options and like the idea of using a battery combiner, as it may keep the starter battery topped-up nicely.

I've seen a kit for sale on eBay using the Victron Cyrix-CT but it says it's suitable for 75ah to 220ah leisure battery(s)

I've got a total 300ah leisure battery so would this still work? I thought this would be irrelevant but you may know better?
 

RAW

Full Member
Although I wonder wouldn't it be better (certainly cheaper) just to have a Voltage sensitive Split Charge relay and then it would take power from Leisure side and input to the Engine Battery consequently trickle charging it, if LB Voltage is greater than engine battery voltage, it would not effectively "balance" anything though as would be a simple solution.
 

Pugwash69

Full Member
My understanding was the vs split charge relays are one way, from starter to leisure? The combiner supports two way. I'll read the pdf again and see if I'm typing nonsense :)

My solar and hook-up both charge the leisure batteries. The van is usually parked under a tree at home but on hook-up, so it would be ideal for it to also keep the starter battery charged.
 

wildebus

Full Member
I was just reading the document by Wildebus about split charge relay options and like the idea of using a battery combiner, as it may keep the starter battery topped-up nicely.

I've seen a kit for sale on eBay using the Victron Cyrix-CT but it says it's suitable for 75ah to 220ah leisure battery(s)

I've got a total 300ah leisure battery so would this still work? I thought this would be irrelevant but you may know better?
There are two basic versions - the CT-120 and the CT-230. Either will work for your setup and be fine. The difference is the current capability as you would have guess. You only would need the CT-230 if you have an upgraded Alternator that can output more current. And even then, there is only so much current a battery can accept - your 300Ah Bank would not really want more than around 75A (25% of total capacity) anyway and quite possibly less.


My understanding was the vs split charge relays are one way, from starter to leisure? The combiner supports two way. I'll read the pdf again and see if I'm typing nonsense :)

My solar and hook-up both charge the leisure batteries. The van is usually parked under a tree at home but on hook-up, so it would be ideal for it to also keep the starter battery charged.
just about all VSRs are bi-directional and will turn on if EITHER side as a voltage greater than the turn-on voltage.
The Victron Cyrix-CT is also bi-directional so has the same benefit of batteries charging via Alternator OR Solar/EHU, but has the extra feature of having the Start Assist (forces the relay to engage) and has a 5 year warranty as well.
The Cyrix is more expensive than a basic VSR but not significantly more (my Cyrix kits are £20 more than the Basic VSR kits and also include the Start Assist kit within that price)
 

Squiffy

Full Member
I've been perusing a couple of posts on batteries and charging systems etc, there seems to be a concern about cab/starter batteries, which I can not really understand as to why folk would want to gang cab and liesure batteries together, I have a system where if absolutely needed I can switch low ampage supply to the hab from the starter battery which I hasten to add that in five years I've never had to do in anger though of course I have tried it out on occasions just to make sure it is working ok ( Sargent unit )
I can also say that the cab/starter battery after five years is still going strong and has never gone below 12.6volts when the vehicle has been left for sometimes weeks at a time, I suppose in the next few years it might start showing signs of degeneration if I still own the vehicle that is but non the less I feel that there is far to much thought and effort being wasted on designing systems that really are not necessary. Well that's my view I can only think that folk want to do these things because its possible and not because it is particularly useful 🙄Phil
 
  • Like
Reactions: RAW

Pugwash69

Full Member
On my previous van, an LDV Maxus, the starter battery goes flat in a few weeks if unused. I don't know if there's some sort of drain I'm unaware of. On my Iveco Daily I've got an Android headunit and I suspect it's only on standby mode when inactive, so if I can guarantee the starter battery is topping up it'll save me keeping a maintenance charger connected over winter.
Thanks for all of the advice though! I've decided to go for the Cyrix-CT kit. I did price up parts to fit one myself but it was near enough the same price as a kit with enough cable and all the right connectors.
 

trevskoda

Full Member
My understanding was the vs split charge relays are one way, from starter to leisure? The combiner supports two way. I'll read the pdf again and see if I'm typing nonsense :)

My solar and hook-up both charge the leisure batteries. The van is usually parked under a tree at home but on hook-up, so it would be ideal for it to also keep the starter battery charged.
Here you go for solar duo charging
solar duel a.png
 

trevskoda

Full Member
If you just want to link batterys for starting if eng battery low or running of ehu charger which only does les batterys then you require a 200ah relay and a dash mount switch as dia.
battery link.png
 

Pugwash69

Full Member
The weird thing on the Maxus was when the battery went flat, it added 800k miles to the odometer! It gave the tyre fitters a shock when they made a note of it.
It's not my only concern, I also want to charge the leisure battery whilst travelling.
 

trevskoda

Full Member
The weird thing on the Maxus was when the battery went flat, it added 800k miles to the odometer! It gave the tyre fitters a shock when they made a note of it.
It's not my only concern, I also want to charge the leisure battery whilst travelling.
Thats simple ,one relay linked battery to battery ,earth small wire input and other spade take of to altanator red signal wire,or just a switch as other post ,then you can if stuck start the engine from all batterys.
 

RAW

Full Member
My understanding was the vs split charge relays are one way, from starter to leisure? The combiner supports two way. I'll read the pdf again and see if I'm typing nonsense :)

My solar and hook-up both charge the leisure batteries. The van is usually parked under a tree at home but on hook-up, so it would be ideal for it to also keep the starter battery charged.
Check out the data sheet on this one and i think you will find it bidirectional
 

wildebus

Full Member
Check out the data sheet on this one and i think you will find it bidirectional
Generally speaking, a B2B split charge solution is always preferred over a a Relay-based system. If you were offered a free choice of one or other, you would go B2B.
However .... There are two key advantages of a VSR based Split-charge system over a B2B:
1) Cost. A VSR system will typically be in the region of £200 less than a B2B system
2) Bi-directionally. The VSR allows you to maintain the starter battery when stationary as well as providing charge to the leisure battery when travelling.

It eliminates the need for a 'battery master' unit that some manufacturers fit, and some owners retrofit, to their vans. It is also more flexible and useful than a solar controller with a secondary battery output as it will operate with both solar AND Hookup.
Note this is for a VSR unit (also the Victron Cyrix-CT), and NOT the switched relay. The switched relay is generally wired to be activated on either ignition-on or alternator running, so will not come on when there is solar or hookup charging.
 
  • Thank You
Reactions: RAW

trevskoda

Full Member
Check out the data sheet on this one and i think you will find it bidirectional
No its a one way diode blocked relay which is well over priced,a 200 ah relay is around £5
 

Attachments

  • relay a.png
    relay a.png
    50.1 KB · Views: 119
  • relay b.png
    relay b.png
    50 KB · Views: 120

wildebus

Full Member
Trev. If the comment about a one-way diode is about that PPT VSR, you are wrong. It is 100% Bi-directionally activated.

The relay you have in the screen shot will need some kind of manual switch or additona! Circuitry if you want it to come on without the engine running.

The requirement discussed is for a way to automatically charge the starter battery from solar OR hookup. Keep up, now ;)
 
  • Like
Reactions: RAW

RAW

Full Member
No its a one way diode blocked relay which is well over priced,a 200 ah relay is around £5
Check datasheet as it works both ways but is voltage dependent so as @wildebus says where it is installed on Sylvia it charges both sides when van is started and running and charges both sides when van is plugged in via 240 and charges both sides when on solar assuming that the battery voltage on side a is greater than (from memory) 13.7V then it will open relay to distribute current to side b....
 

Users who viewed this discussion (Total:0)

Top