Help! Is my EHU actually charging my batteries?

Pudsey Bear said:
I went and put it on 24/7 yesterday afternoon, I have plug in meter to check power usage so I'm leaving that few days to see what it uses.
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Is it worth leaving a charger on full time/part time to keep your Cab battery's life extended?
You have to balance the annual running costs of the charger against the life extension of the battery and the cost of a replacement battery. Also the availability of solar, your energy tariff (E7 etc), standby/trickle charger consumption, initial cost of the charger, etc will skew the equation, not to mention factoring the risk of the charger going faulty.
Assuming a 7W continuous mains consumption (just a guestimate on my part) and a 51p/unit cost that gives a cost of over £30 a year, last time I bought a cab battery it cost me £65 four tears ago.;)
 
Okta said:
and not enough volts is lack of water pressure so you only get a trickle even with the tap wide open.
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The problem with the 'water tap analogy' is that there is a very high pressure in the water mains so like all analogies that use the water to explain electrical theory, it fails at some point. Turning down the tap to a trickle doesn't lower the pressure(Voltage) of the supply, it only lowers the pressure of the delivery inversely proportional to flow(current) . Eventually the bucket still gets full and starts to overflow.
Much better to use the 'two water tanks analogy' where the water level (voltage) in the 2nd tank can never exceed the level in the 1st tank and they are always trying to balance each other out. Google it.
 
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merl said:
Is it worth leaving a charger on full time/part time to keep your Cab battery's life extended?
You have to balance the annual running costs of the charger against the life extension of the battery and the cost of a replacement battery. Also the availability of solar, your energy tariff (E7 etc), standby/trickle charger consumption, initial cost of the charger, etc will skew the equation, not to mention factoring the risk of the charger going faulty.
Assuming a 7W continuous mains consumption (just a guestimate on my part) and a 51p/unit cost that gives a cost of over £30 a year, last time I bought a cab battery it cost me £65 four tears ago.;)
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last time you bought a cab battery, electricity was nowhere near 51p/unit (it is not that near to it even now ;) )
 
merl said:
The problem with the 'water tap analogy' is that there is a very high pressure in the water mains so like all analogies that use the water to explain electrical theory, it fails at some point. Turning down the tap to a trickle doesn't lower the pressure(Voltage) of the supply, it only lowers the pressure of the delivery inversely proportional to flow(current) . Eventually the bucket still gets full and starts to overflow.
Much better to use the 'two water tanks analogy' where the water level (voltage) in the 2nd tank can never exceed the level in the 1st tank and they are always trying to balance each other out. Google it.
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would that be the "Balancing Vessels"?
 
I might have helped if I'd turned the power back on after plugging in the meter of course.

Now on :rolleyes:

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merl said:
Is it worth leaving a charger on full time/part time to keep your Cab battery's life extended?
You have to balance the annual running costs of the charger against the life extension of the battery and the cost of a replacement battery. Also the availability of solar, your energy tariff (E7 etc), standby/trickle charger consumption, initial cost of the charger, etc will skew the equation, not to mention factoring the risk of the charger going faulty.
Assuming a 7W continuous mains consumption (just a guestimate on my part) and a 51p/unit cost that gives a cost of over £30 a year, last time I bought a cab battery it cost me £65 four tears ago.;)
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34p Kwh here, and the charger will not be charging 100% of the time hopefully, a new 100ah VB will be well over £100, I already have the charger and it can be used on any battery up to 110ah. assuming the 7w is correct the 365 figure will be £21.90p

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I just had to go up to the farm for some Heggs and I looked in the van to see what I'd used so far.

I didn't have my phone so no pic but it now reads 0.080 and it's 5.57 minutes of usage, no idea how much that is in £s but it might still be ramming in the amps so I'll leave it until next Monday to see weeks power usage and consider if it will be ok left on or maybe 12 on and 12 off or something.

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Pudsey Bear said:
I just had to go up to the farm for some Heggs and I looked in the van to see what I'd used so far.

I didn't have my phone so no pic but it now reads 0.080 and it's 5.57 minutes of usage, no idea how much that is in £s but it might still be ramming in the amps so I'll leave it until next Monday to see weeks power usage and consider if it will be ok left on or maybe 12 on and 12 off or something.

1678100698370-jpeg.118120
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I hope not Kev, that's nearly 4 grand a year!!
 
RSD7a said:
I've just replaced a Banner 3 yr old lead acid that appeared to be no longer holding charge. I made a conservative choice and stuck with lead acid via Alpha batteries and got a 110 AH expedition plus, semi traction.
Now after a day charging this new leisure bat via EHU and a day charging Vehicle battery, it seems like no extra charge has been delivered to either.
eg the new leisure battery shows full charge on the Sargent control panel, but drops back one notch as soon as I switch interior lights on. That's exactly a symptom I had with the battery I've just taken out. In the past when all was working well, the fully charged lights on the control panel rarely dropped at all.
I've checked all fuses on the Sargent EC155 and all seems in order.
How can I check if the charger is actually providing charge to the batteries?
(I've a solar panel which appears to be charging a bit in the dim Scottish daylight, but does this confuse any diagnosis?)
Any thoughts please?
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Put a multimeter across the battery!
A fully charged battery at rest is around 12.8v. Plug in the mains, and check the voltage again. It should jump to 13.8v to 14.5v depending on the battery’s state of charge.
 
It should be 5:57 I see what you mean silly colon not a full stop, the joy of posting from a phone.

I'll have a look again about the same time today to get a 24 hour figure and I'll see if I can put the tariff in and restart it.
 
after 23:50 minutes ;) ;)

But the online calculator is way off
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£1.86 must be wrong but I set it to 0.228 Kwh (as per the display) @ 34p for 24 hours. so it must be only 0.22 Watts which makes more sense
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Just a general comment .... when a motorhome is parked up, why have a battery charger on the starter battery anyway? the more important battery in terms of value is the Leisure battery. Does that have a battery charger in it as well? (if not it should do).
It makes much more sense to concentrate on keeping the leisure battery maintained, be it via EHU or Solar, and then using some kind of method to use that same power to maintain the starter battery at a good level. That method can be a manual one, such as a simple cable (fuses each end for safety) between the starter and leisure batteries, or an automated one, such as a Batter Master or similar, or ideally an Ablemail AMT12-2, which is programmable so you can configure to precisely your own requirements.

There are good reasons to keep a starter battery in a charged state, and it is not just financial. The comment, slightly tongue in cheek (I hope!) that seemed to suggest it is cheaper to just replace the battery than spend the money on charging it over a period of time, was silly and for some reason this thread has started to go down a path of working out the equivalent costs to compare. That may be an interesting excercise possibly, but so flawed it is pointless.

Reasons to maintain the Starter Battery
1) so you can use the vehicle when you want
2) to avoid a potential large repair bill if you let it decline and try and start the engine with a low voltage. This is a very real issue on some Ducatos (and likely other Sevel vans) which should not be ignored.
3) avoid buying a new starter battery prematurely as it has been left to discharge too low

Reasons not to maintain the Starter Battery
1) ?


Cost of maintaining the Starter Battery
1) If you use a Mains Charger, cost of charger, plus the electrical overhead of the power used
or:
2) cost of a piece of cable and two fuse holders (manual maintenance method) as you are (or should be) maintaining the Lesiure Battery anyway
or:
3) cost of a Battery Maintainer/DC-DC Trickle Charger (automated method) as you are (or should be) maintaining the Lesiure Battery anyway

Cost of additional power to maintain the Starter Battery
1) If it was maintained by excess power from Solar, that would be £zero.
2) If it was maintained via the Mains Charger to the Leisure Battery, then you can base the cost roughly on the extra power taken by the trickle charger to send to the Starter Battery. Each van will vary, but in my own case (I just looked now to check the last 12 hours), the Starter Battery is taking around 5Ah/Day to maintain it at around 12.5V. More than I expected, but that is the number.

5Ah/Day at a nominal 12.5V is 62Wh/Day. Over a year (so you have not used the vehicle for a full year), that works out to be 22.6kWh/Annum.
22.6kWh at 50p/kW (we will assume that rate) will mean maintaining the Starter Battery at a healthy state for a year has cost £11.30 for the year. This would be worse case scenario as if you have solar, the solar would be doing the work for a reasonable period and that maintanance has no additional energy cost. Assuming you are using the vehicle sometimes (!), there is no maintenance needed during that time.
A more likely cost for this starter battery maintenance might be around £6/Annum to include a Winter Layover period with no use and poor solar


Ok. For those who just want to jump to the TL: DR summary ....
DO NOT USE A CHARGER ON THE STARTER BATTERY OF A MOTORHOME. GET A DC-DC BATTERY MAINTAINER AND LET THE STARTER BATTERY CHARGE VIA THE LEISURE BATTERY CHARGING SYSTEM

and if the reply is "I am not charging the Leisure Battery", then the answer to that is "Why the hell not if you think you need to charge the Starter Battery?"
 
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