Batteries off grid - my findings - my fix

Discussion in 'Motorhome Chat' started by Don Quixote, Aug 25, 2014.

  1. Don Quixote

    Don Quixote Funster

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    Morning, I thought I would give my batteries a good "bashing" whilst in the UK for 3 weeks and would like to share with members on here my findings as I have read all the posts on here about "my battery is dead" or "why is my onboard charger not changing my battery" or "why does my engine not charge my batteries whilst running parked up"

    Firstly I have the following:

    (a) 3 x 110amp hour battery - These are in good condition and hold charge well.

    (b) Victron BMV 600S - This is by far the best thing for monitoring your 12 volt system.
    [​IMG]
    (c ) CBE charging system as fitted by MH manufacture - After many hours of searching the CBE system I have 2 x Safety relays EPC they are both in front of the CBE box.
    Photo:
    [​IMG]
    [​IMG]
    The inside of the case with the relay, fuse 50Amp (power circuit) and one 5 Amp. (Control circuit relay)

    (c) Solar panel 80watts - A 80 Watt solar panel will give you about 320 Watt-hours of energy on a summer day. For a 12 volt system, that corresponds to 26.7 Amp-hours put back into your battery bank each day. On sunny days, you will get more; on overcast days you will get less. So in Winter, your 80 Watt solar panel will only be giving you about 80 Watt-hours of energy per day in the worst case. For a 12 volt battery, that corresponds to 6.7 Amp-hours put back into your battery bank each day .
    (d) Ctek MXS 25 main charger - This runs off mains supply (EHU) or gene ( no problems with 10i ) It will start off charging at 14.6 and drop down over a period to 13.5 - start up can be 16/18amps then down to 0.1 amps depending on how long you run the gene for. I have found that after 2/3 hours the batteries are charged with NO load on the batteries.
    [​IMG]
    (e) Honda 10i Generator - This was bought after being recommended by many people as being the best out there. To date I have used it a handful of times, however over the past week it has been on most nights for this test.
    [​IMG]
    Findings:

    A typical night parked up we would have a few LED lights on the TV and Sat system with tuner box. At most about 4.5amps for 4/5 hours and as and when the water pump ( for cuppa etc ) so quick 3/4 amps. The batteries lasted first night no problem and the second, however by the third night voltage is around the 12.4 mark, that is without moving or charging. During the day here in the UK the solar panel is at best just taking up room on the roof. So happy enough I thought the batteries and charging system were doing what they should.

    Now as many on here think - no problem, I will start the engine and that will charge the batteries whilst I'm parked up....... NOT so as such because it takes hours of engine running just to add a few amps. A battery needs about 120% INPUT to get to full charge...so...your 110 leisure battery/batteries would need: 110 x 120% = 130Amps per hour. I have 3 x 100!!! Normal charging rate is at 10% for best life...SO.....13A for 10 hours and as most alternators will charge....14.2 - 14.4V at about 2000rpm it will drop the amps from 5/6/7/8 at start to 0.2 after 1 or 2 hours of running. So after that you are only trickle charging so that when you park up the batteries look good for about 1 or 2 hours and then the voltage drops very quickly. At this point many think that their batteries are destroyed because they wrongly or rightly think the run/drive should have charged/them.............

    So running a gene would resolve the problem....... well sort of.... the gene can only put in xxx amps so the same effect happens unless you're running it for hours on end ( not recommended in a busy location - at best you will annoy people off at worst it will get stolen! ) so I thought why not try a........

    CTEK MXS 25 Mains charger which would work whilst on EHU and for use on the generator. Well it works great on EHU conditioning the batteries and can on the generator charge the batteries in 1/2 hours ( with NO LOAD ) pushing into the batteries 14/16/18 amps depending on state of charge, however again the generator has to be run. Please note I do not use the word "fully" as the following conditions apply: 2 hours at 10A = 20 - 5 hours at 5A = 25 - 10 hours at 3A = 30 and 20 hours at 1A = 20 (The last one is your engine running! )

    So now what next.......... Well if you're never "off grid" you have nothing to worry about. If you are "off grid" once in a blue moon again you have nothing to worry about as in both cases your on board charger will sort things out for you as soon as you return to EHU.
    If however you plan to use your MH without paying for the privilege of EHU then I hope the above helps you understand that in the case of 12 volt you need more than the standard charging system fitted to most motorhomes.

    Keeping your batteries charged off grid is a bit of a black art and as many do not fully understand the charging system that they have fitted in the motorhome I thought my findings might be of use to others ( don't forget the like button )

    I have ordered a sterling battery to battery charger and hope to fit it before leaving the UK to head back home to Spain, but I'm not too worried if I don't. My plan is to get rid of the gene as carrying it means carrying petrol too.

    I will update this post when I have had the sterling battery to battery charger fitted and tested.

    Any feedback on the sterling battery to battery charger from those who have fitted it would be great and even better if you have fitted it with a CBE system.

    Thanks for reading.
     

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    Last edited: Aug 25, 2014
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  2. irnbru

    irnbru Funster Life Member

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    Wow. What a great post. Think I might need to re read it several times before I fully understand it. Thanks for taking good the time to write it and look forward to your update.
    There is no thanks button anymore.
    THANK YOU.
     
  3. Don Quixote

    Don Quixote Funster

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    Changed the thanks to like, ta. It is such a "gray" area I thought many would like to at least have an understanding about their charging system. Thank you.
     
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  4. Jim

    Jim Ringleader

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    Since installing the Sterling Battery to Battery charger, along with a 2100w Inverter, I have not had cause to run our Honda Generator at all. This year at some rallies the Funster band have been using power straight from our two 110 Banner batteries through the inverter. Should the band get too many encores (a common occurrence) I know all I have to do is run my engine a little while and the batteries are back to 85/90% very quickly (y) Who needs a genny, who needs the sun. You just need a B2B- for me its perfect.
     
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  5. Baycott

    Baycott Funster

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    Great post John. Thanks for taking the time to let us know your findings. We are going to change our van soon and hope to have solar/inverter and b2b fitted so we can do more wild camping (y)

    John
     
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  6. Don Quixote

    Don Quixote Funster

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    Well I would not have a solar panel fitted ( unless going sunny places a lot ) if you're going to have the sterling battery to battery charger fitted as it will do everything you require and you will not be adding weight that you do not need. The inverter on the other hand is a must for the wife hairdryer............
     
  7. jonandshell

    jonandshell Funster

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  8. Don Quixote

    Don Quixote Funster

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    Very interesting read on your fitting a Sterling 160amp Alternator to Battery Charger. I have gone for the 12-12V Battery-battery 50A digital charger because I liked the "simple" fitting area, however your post has answered my question about transit fitting and no vehicle mods at all, so it should work fine with my CBE charging system. I can I think if needs be remove the CBE charging system by removing the fuse from the charging system as shown above.
     
  9. jonandshell

    jonandshell Funster

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    Does your Transit have the single or twin battery configuration?

    This will determine how your leisure batteries and CBE electrical system is wired in.
     
  10. jonandshell

    jonandshell Funster

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    You will need to fit an isolating relay to your leisure battery bank in order to ensure your B to B will charge correctly.
    You can't just simply remove the split charge fuse because your fridge and habitation electrics will draw from the B to B too, reducing its charging current to the leisure batteries.
    Simply put a 70 amp five pin relay between your leisure batteries and the CBE panel B2 terminal. Use an ingn or D+ feed to the coil and use the normally closed contacts to connect the batteries.
    When the engine runs, your leisure batteries will be connected solely to the B2B charger. Meanwhile, the original split charge relay will supply all your habitation electrics and fridge.
     
    Last edited: Aug 25, 2014
  11. Don Quixote

    Don Quixote Funster

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    Jon now
    You have me thinking.... as there are so many CBE systems my understand is that the one fitted by the Benimar / Chausson has 2 x Safety relays fitted. I have not looked to much into them yet, but my understand is one is for the battery (a) vehicle battery (b) leisure battery. Therefore as long as I connect to vehicle battery to the sterling changer it should be fine, but this is new to me so at this stage more reading is needed. Thank you for the help.
     
  12. GJH

    GJH Funster Life Member

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    Very interesting and my thanks as well. I was particularly interested in the solar panel figures:
    We have a 80W panel and 80Ah battery which we find adequate year round but I had never worked out the figures. We don't have a TV or satellite system and the fan for the blown air heating is pretty efficient so it would be unusual for us to use more than about 6 or 7 Ah in a day.
     
  13. Don Quixote

    Don Quixote Funster

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    Graham, you don't say which blown air system you use. We have the Webasto Diesel system and when that boots up it can draw 7/9 amps whilst it sorts itself out and then drop down to 1 or 2amps blowing around the MH and then draws 7/9 amps to shut down. In Spain we never use it, but over the past few days it's been working away. Even if you're only using 6 or 7 amps a day that means you need 18 to 21 amps back to fully charge your battery not just top it up. This is the problem as many think..... the solar panel is working and fully charging the battery. It is not and over time the battery needs a full charge to make it work correctly or die. Hence my post so people can understand that in many cases the charging system fitted is not up to the job. Many go in EHU and park up for 2/3 days and this is where it does the job as it takes 2/3 days to fully charge battery/batteries.
     
  14. longdog

    longdog Funster

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    Excellent informative post, can we make this a "sticky" please?
     
  15. bungy

    bungy Funster

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    We have exactley the same set up in our chausson, when I fitted our b2b I looked at the extra relay fit from jon, but after much tinkering found it wasnt needed as the two security relays did the same job, and it works well.
     
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  16. Don Quixote

    Don Quixote Funster

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    Ah....... perfect may I ask then did you just fit it and forget. Did the security relays work in that one or both could see the charge coming in and stopped/reduced the charge from the CBE unit. It should arrive tomorrow, but need to get cables as well looking at 25 mm sq from to battery. Thanks for the info.
     
  17. GJH

    GJH Funster Life Member

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    It's the Trumatic C3402 John. Takes a couple of amps for a short while when starting then virtually nothing. The van is pretty well insulated so we don't need to use a lot of heating.
    All the electrics are through an Elektroblock EBL99 (solar panel wired direct into it) so no need for any other B2B arrangement.
     
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  18. bungy

    bungy Funster

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    I did have issues with the extra relay fitted, control panel and fridge were throwing intermittent wobblies. But since removing it all is well.

    Having pawed over the wiring diagram for the van for hours and doing testing with a digi meter I found that the 2 relays did a similar job, and each was specific to either the cab or hab bat

    In ours s1 controls the charge from the cbe charger on 240v to the cab battery, once the hab is full and s2 controls the charge to the hab battery from the alternator via the cbe, both voltage sensing. So on the move s2 only opens when the cab batty is fully charged and the hab bat is below a certain voltage (not sure what though!!) All other 12v wizardry on the move such as the fridge is controlled by the main cbe charger panel (quite a good piece of kit.. and whilst im not 100% sure it may even act as a solar controller too!!)

    Only snag I had was the cab and hb bats being at opposite ends of the van!!. I opted for putting the b2b as close to the cab bat as possible and using a hefty 800amp lorry jump lead to wire up to the hab bat at the rear.

    Only taken an hour to get hab bats from 70% to fully charged today on a run back from a weekend away.

    So yeah...fit and forget:)
     
  19. tonyidle

    tonyidle Funster

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    Not mentioned as far as remember is the need for more than 80W on the roof. I've been off-grid in the Midlands for 12 days so far and my batteries are fully charged by the end of the afternoon each day. I have 3 x 110Ah batteries and 230W on the roof. I use an MPPT solar regulator in conjunction with the Hymer charger. The Hymer charger allows any charging source to keep the starter battery ready for use and contains elements of B2B charging when the van is being driven. So far it all works well. My laptop use is fairly heavy although we don't use the TV much (around two hours in 12 days so far). All interior lights are LED.
     
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  20. Snowbird

    Snowbird Funster Life Member

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    A very interesting thread. What I dont understand is this. On all the vans I have owned in the last few years I have had 330 amp battery banks with around 300 watts of solar. I have used the vans for periods of up to 3 months without hookup, and have never had a problem with flat batteries. The van I am running at the moment has a 330 amp battery bank with 250 watts of solar. It does have 2 alternators fitted to the engine as the engine is 24 volt. The 12 volt alternator is just for the habitation side so I presume this works much the same as a B2B, but am not sure. I do have a type of battery fuel gauge fitted which tells me the battery voltage, amps left, amps drawn etc and the 330 amps have never fell below 220 even after a few days without much sun. All 12 volt wiring is through a shunt, so I can tell immediately what is going in and out and also what is left. I dont see how I can improve on this system, but am open to suggestions.
     
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