Charging Main Battery from EHU?

[Dieseldonkey]

... Not sure what it does about keeping the 20% headroom for regeneration. Don’t have my head round that yet.

I'm sure I saw a similar train of thought in another thread somewhere. Does it simply not mean the charging voltage/current form the alternator just wont get ramped up during breaking, until the voltage monitor determines that the vehicle battery is back down to 80% or so. Cant see it doing any harm to charge to 100%. I'm sure someone will pick me up, if I've got that wrong though.

 

[Farnorthsurfer]

I'm sure I saw a similar train of thought in another thread somewhere. Does it simply not mean the charging voltage/current form the alternator just wont get ramped up during breaking, until the voltage monitor determines that the vehicle battery is back down to 80% or so. Cant see it doing any harm to charge to 100%. I'm sure someone will pick me up, if I've got that wrong though.

Yes I expect you’re right there, i don’t think it I’ll do any harm and will balance itself out in use.
Like you I have a twin slider and am shamelessly planning to copy some of your ideas there is in fact a 160w panel sitting in the van as I type on it’s way to meet a Jerba rising roof in the morning.
I can’t sleep, like waiting for Santa! Can I get NHS counselling I feel I see them cut the roof off?

 

[travelvolts]

Both leisure and vehicle battery are negative earthed to the van. As I understand it, the voltage monitor is on the negative side. Anyone see any issue with simply running a jump lead from the positive leisure battery terminal, to positive terminal on the vehicle battery, if a jump start is required.

Just check that your leisure battery negative cable is of sufficient size before you try that!

 

[Martinf]

@Dellmassive described the possibility of a B2B charger for topping the Van battery up from the Leisure.

you could use a Diode based reverse charge box "standby charger" ( as @t0mb0 mentioned) like this: https://amzn.to/2v6FPdb

I would like to have use of something like this Votronic unit; referring to some of my earlier postings saying I was having trouble keeping my Van battery up. However I note that the Votronic instructions stress that it should not be used for a Lithium LiFePO4 leisure battery to Lead van battery. Is there a reason for this, or a way round it? Can it be installed with a switch in the line so it is only used when the Van is parked? Or perhaps used in a wire across between the two different 12V outlets, again only when parked?

Or considering the enthusiasm for Lithium LiFePO4, is there an alternative that will work?

 

[Dellmassive]

The reason is that a lithium rest voltage is way over 13.5v when charged..... and SLA is way lower.

Because it's just a diode an a box with an inline current limiting resistor it works on the principle of the 0.6v drop across the diode.

The lithium will always be higher..meaning that it will always s be charging at max rate to equalize the batterys..... which it never will as the rest voltage is so different.

Though saying that I can't see any reason why it could not be used as a temp plugin fix or have running on a temp switch for a few hours....?

The Ctek and Renogy dc-dc can reverse charge the starter from solar.

You could use a small stand alone smart 240v smart charger if on EHU...... or maybe have that run off a small inverter (via the lithium).? To back charger the starter.

Or you could try a small dc-dc charger..... just plugged in when needed.

I supose it depends on the use case.?

Are you looking for an "off grid" solution..?

 

[Martinf]

@Dellmassive many thanks for the information.

I have back charged the Van using my CTEK MXS 5.0 charger when on hookup but have not yet needed to do so off my inverter. I could do that but presumed a direct nominal 12V connection would be more efficient with no inverter losses.

So I was looking at off-grid options, effectively to use the roof mounted solar input rather than my much smaller panel that I can connect to the Van battery.

Is there a specific CTEK or Renogy unit that can be wired in or used ad-hoc? Would the Votronic unit be suitable on an ad-hoc as needs basis, or would the voltage differential be too much? Incidentally my battery/ solar controller is the NDS Power Service Gold which specifically does not back charge.

 

[Dellmassive]

these both reverse charge the starter battery when the aux battery is full . . . . from solar only. + work with Lithium.

Renogy 50A DC-DC On-board Battery Charger with MPPT - https://amzn.to/2QeITur

CTEK D250SE DC-DC + MPPT - https://amzn.to/2TAzMYx

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I have back charged the Van using my CTEK MXS 5.0 charger when on hookup but have not yet needed to do so off my inverter. I could do that but presumed a direct nominal 12V connection would be more efficient with no inverter losses.

- that would be the case regarding efficiency, but with the lithium being much higher volatge its worth a try.

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you could just try adding this as a addhok temp plugin - https://amzn.to/2uxXc6b

or Votronic 3324 Battery-to-battery charger VCC 1212-30

with this idea, you would have to have a switch or plug to ensure its only operational when static or engine not running to prevent a current-loop from the seconf dc-dc charger.

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or you could try running 2xMPPT controllers from one solar array . . . (one powering each side starter/Aux battery)

I've not done this yes, but have 2x victron MPPT controller ready to setup a test when the sun is back.


edit: looks like this question has been asked before: Multiple charge controllers on the same solar panel


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[Dellmassive]

have a look here: Split Charging Guide - caravans, campervans, motorhomes, boats, vehicles

heres another option . . .

The Voltronic DUO - https://amzn.to/2Gvj3xH



"The MPP-series controllers feature a second output so that some of the solar power can be used to trickle-charge a starter battery with a current of 1A max."

• Nominal operating voltage: 12V DC
• Solar module max. output: 250W
• Solar module max. current: 15A
• Solar module max. open circuit (OC) voltage: 50V DC
• Max. charging current: 17.5A (aux) / 1A (starter)
• Compatible battery types: Lead-acid (flooded, sealed), Gel, AGM, LiFePO4
• Stand-by current consumption: 0.004 A
• Over-charge protection: Yes
• Reverse current protection (back drain at night): Yes
• On-board mains suppression filter: Yes
• Number of charging ports: 2
• Protection against over-load, over-temperature, short-circuit: Yes
• Connection for temperature sensor: Yes
• Compensation for voltage loss on charging cables: Yes
• Connection for remote display panel: Yes
• Operating temperature range: -20 to +45°C
• Overall dims incl. mounting flanges: 131 (W) x 40 (D) x 77 (H) mm
• Weight: 235g
• Manufacturer's article number: 1715

Part Number: MPP250

 

[Dellmassive]

looks like there is 4x versions goin up in charge current.


Votronic, MPPT 165 Duo Digital charge controller - https://amzn.to/2Gr4g7q

Votronic, MPPT 250 Duo Digital charge controller - https://amzn.to/2sXG6hC

Votronic, MPPT 350 Duo Digital charge controller - https://amzn.to/2t4lGnm

Votronic, MPPT 430 Duo Digital charge controller - https://amzn.to/2O1yGkP



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https://www.votronic.de/images/Manuals/07. Solar Current Technology/1710_1715_1720_1725_e.pdf

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looks like it has LTD (low temp) too . . .



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[Tsixty]

This time of year I've always been in the habit of sticking both our vehicles on a battery charger every 6 weeks or so as we do a lot of short journeys and very few long runs, that's been even more the case this year. I've used my trusty Ctek MXS10 for this purpose many years running. I like to keep a healthy topped up battery during the winter.

Anyway, did our Kuga, which took around 5 hours for the charger to go into its float mode indicating that the battery is fully charged. That's pretty much what I would have expected.

First time I have gone through this process on the T6. Went to check after 5 hours, charger was still in the main charging phase, checked a couple more times and even at 10 hours it still wasn't indicating a full charge. I had to give up and lock up.

I haven't had any low battery symptoms so am surprised a 10amp charger hasn't fully charged a 75ah battery in that time. Could this be an early sign of a developing fault with the battery i.e. it can't actually get to a fully charged state? Assuming it is the original battery, it is 18 months old Varta AGM type.

 

[Pete C]

I had this just once with my Ctek 5A charger. I put it down to the charger getting confused, and not switching out of full charge mode. I turned it off and on, reconnected it, and it worked fine after that.

Pete

 

[Tsixty]

I had this just once with my Ctek 5A charger. I put it down to the charger getting confused, and not switching out of full charge mode. I turned it off and on, reconnected it, and it worked fine after that.

Pete

Thanks had tried that, didn't seem to make any difference.

What/where is the best body earth around the battery area? I'm wondering if where I chose wasn't very good, it must have been an actual earth as the charger shows when it is properly connected, but perhaps it just was not a very good earth?

 

[Phil_G]

This time of year I've always been in the habit of sticking both our vehicles on a battery charger every 6 weeks or so...

There are many posts here reporting flat batteries after much less than 6 weeks - I'd suggest 3 weeks max. Theres a lot of electronics cr4p hanging off the battery when static, and intelligent chargers are easily fooled by batteries having a constant discharge load, as is the case with your T6 - during the CV stages the charger expects the current to taper off to a very low value but background discharge prevents this happening.

...after 5 hours, charger was still in the main charging phase, checked a couple more times and even at 10 hours it still wasn't indicating a full charge... so am surprised a 10amp charger hasn't fully charged a 75ah battery in that time.

Bear in mind that a 10A charger doesnt 'push' 10A into your battery. After 10 hours it would probably be either on absorption sat around 14.4v or on float at 13.8v and very little charge current would flowing in either case. To be sure you really need to check with a voltmeter. After 10 hours what numeric stage was the MXS10 showing?
Cheers
Phil

 

[Tsixty]

There are many posts here reporting flat batteries after much less than 6 weeks - I'd suggest 3 weeks max. Theres a lot of electronics cr4p hanging off the battery when static, and intelligent chargers are easily fooled by batteries having a constant discharge load, as is the case with your T6 - during the CV stages the charger expects the current to taper off to a very low value but background discharge prevents this happening.

Bear in mind that a 10A charger doesnt 'push' 10A into your battery. After 10 hours it would probably be either on absorption sat around 14.4v or on float at 13.8v and very little charge current would flowing in either case. To be sure you really need to check with a voltmeter. After 10 hours what numeric stage was the MXS10 showing?
Cheers
Phil

Thanks for helpful input.
That's my point though; the MXS10 is still at stage 4 after 10 hours on a battery that wasn't flat or causing any issues like poor starting.

 

[Keeff]

I got one of these from eBay as my battery was playing up. It gives you a lot of info about the battery and charging from the van.

 

[d bath]

A lot of people use a ‘Battery Master’ type trickle charger to keep the vehicle battery topped up from EHU/solar. Only about £25 usually. Some b2b or solar chargers have these built in.

Cheers - presumably this needs a dedicated set of wires to my main Battery? I presume I cant just use the existing set that take charge from the main battery/alternator to the leisure circuit in reverse when the main Batt is low

 

[travelvolts]

You can if the cables are of sufficient size to minimise volt drop.