Is regular EHU necessary?

[popotla]

My vehicle has an 80Ah AGM starter battery, two Relion LiFePO4 100Ah Lithium batteries, a Vitronic device (Triple) and two 110W solar panels. Is it a good idea (or important) to hook up to the mains periodically? I have heard that this should be done "about once a month" and also, contradicting this, that there's no need to do so.

 

[Badknee]

I have just had to replace two thirteen months old flooded batteries because I’m told I didn’t put them through the ehu cycle that takes them up to 14.6v. Flooded batteries need this apparently.

 

[funflair]

I will happily go right through the summer months without hooking up, we have 320watts of solar and that seems to give the batteries a full charge, if you have some sort of monitoring on your batteries and they say 100% I wouldn't think you could not get much better than that, but on the other side of that if you are constantly taking out and never putting enough back in to get a full charge then yes plugging in occasionally will surely help.

Martin

 

[funflair]

I have just had to replace two thirteen months old flooded batteries because I’m told I didn’t put them through the ehu cycle that takes them up to 14.6v. Flooded batteries need this apparently.

What batteries were they Paul.

Martin

 

[Pugsy]

My trojan t105 batteries are 2 year old now and have never had hook up.i dont even have hook up in my van ,12volt only.
I think it depends on your usage.i am in portugal at the moment but often get the same in the uk in summer,my voltage reads about 14.6 for a couple of hours and then floats at about 13.4v.
I only use leds and a tab no tv at night and my crx80 comp fridge uses around 40ah per 24h.
But i guess if you spend winters in the uk it could be a problem to get your batteries fully charged on a regular basis without hook up.
Just my opinion of course , i know i am really lucky to get away for the winter months..
Cheers Cris.
Ps should mention i have 240ah of battery,epever mppt controler and 300w of solar.

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[Northernraider]

I have just had to replace two thirteen months old flooded batteries because I’m told I didn’t put them through the ehu cycle that takes them up to 14.6v. Flooded batteries need this apparently.

My solar seems to do that , my leisures are at 14.8 just now and will drop down to 13. Something later on.
They are also showing 100% charged , I've only had this van on ehu 3 times since October and only because I don't seem to be getting correct charge from my engine charging.


2 x 110 flooded batteries and 200 watt solar panels.

I only use lights , pump and tv mostly , occasionally heater in colder nights and batteries normally between 85 and 90% each morning

 

[Feltwell]

I have just had to replace two thirteen months old flooded batteries because I’m told I didn’t put them through the ehu cycle that takes them up to 14.6v. Flooded batteries need this apparently.

I understand they need a higher charge every now & then, but surely they get enough of this when you drive the van for a while? After all, flooded batteries are still in the vast majority of cars as starter batteries and they never get a hookup!

I can see that being on a constant low trickle from solar and nothing else probably doesn't do them any good.

 

[tacr2man]

I would say it will be down to the required duration of sun you have
as the mppt controller should have a regime that has levels of voltage and ampage that are programmed to achieve the correct battery maintenance and life . I hope that makes sense ?

 

[DBK]

I would say it will be down to the required duration of sun you have
as the mppt controller should have a regime that has levels of voltage and ampage that are programmed to achieve the correct battery maintenance and life . I hope that makes sense ?

That's my understanding too but I guess not all controllers do it. Victron chargers have a daily cycle which starts, as the name suggests, every morning.

 

[popotla]

Thanks. Your answers lead me to a couple of questions.

On another thread https://www.motorhomefun.co.uk/foru...rly-re-electrical-system.188585/#post-3127480, Paul wrote:

I’ve just had two leisure batteries destroyed because they wearnt put through the three cycles they need. First is on hookup that takes them to 14.6volts. Fully charged on ehu in float mode 13.4v then the third off ehu down to 12.3v
If at all possible hooked up to a generator may help prolong the life of your batteries.

I don't understand this about 'three cycles', maybe someone would kindly clarify it, bearing in mind my regrettably low beginner level in these matters.

Our two leisure batteries are Relion LiFePO4 100Ah Lithium. Does the importance of "three cycles" apply to them?

Also, does the rule of thumb "12.6-12.7V = fully charged; 12.45 =75%; 12.06=25%; 11.89=0%" apply equally to all batteries?

For various reasons we've used our van very little but today are moving into it 'full time' (no previous experience). We plan to be here and there in and around our home town for a couple of weeks, ideally off-grid as much as possible but we can also use a campsite. No sun today and no sign of it but we might be able to maintain battery power with a run or two. Let's see.

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[autorouter]

I don't understand this about 'three cycles', maybe someone would kindly clarify it, bearing in mind my regrettably low beginner level in these matters.

I think there's a bit of a misunderstanding here. I don't know anything about this 'three cycles', unless he's referring to the three phases of a smart charger for lead-acid batteries.

The three phases are bulk, absorption and float. In the bulk phase, the charger puts out the maximum current, and monitors the voltage until it rises to about 14.6 volts. In the absorption phase, the voltage is fixed at 14.6 volts, and the current is monitored until it falls to a preset value. At that point the battery is 100% charged.

In the float phase, the voltage is fixed at about 13.8 volts, which is just a tiny bit above the battery voltage. A very small current, maybe 100 milliamps, is put into the battery to compensate for the natural self-discharge of the battery over time. If some small loads like an alarm, tracker etc are connected, the charger will provide for these too.

Lead-acid batteries include flooded, sealed, VRLA, AGM and Gel. However LiFePO4 batteries are completely different. For a start, they do not self-discharge anything like as much as lead-acid, so there is no need for a 'float' phase to keep them charged over time. The settings for the smart charger are not very different, but it's enough to make a big difference over the years that the battery is in use.

Some of the better MPPT solar regulators also are smart chargers, and have settings for the different battery types.

Also, does the rule of thumb "12.6-12.7V = fully charged; 12.45 =75%; 12.06=25%; 11.89=0%" apply equally to all batteries?

Using the battery voltage to judge the state of charge is kind of OK for lead-acid batteries, if you know what you are doing, although it can be misleading. For LiFePO4 batteries it's a complete waste of time. The voltage hardly drops at all until there's very little charge left, and it's in the range where it might be damaged by excessive discharge.

A proper battery monitor is the only way to know the state of charge of lithium batteries. This continuously monitors and counts the amps going into and out of the battery, and keeping a count of the running total, and working out the state of charge as a percentage. If you're investing in expensive lithium batteries, a proper battery monitor is a must-have.

 

[Reallyretired]

My solar charger has three phases, and is off ehu for six months at a time, and the batteries are fully charged, including the starter battery. In the summer the solar can produce 20A plus which is more than the 18A max of the ehu charger, which is a simple float charger to 13.6v so never fully charges the batteries.
400w solar 30A MPPT controller, can't remember the brand, not one of the big brands.

 

[popotla]

The read-out for my lithium batteries is almost constantly showing 13.1-13.2V (though once down to 13.0). Plenty of sunlight these days for the solar.But is it the case that this is not indicating the real charge? There has been some flashing/flickering.

 

[autorouter]

The read-out for my lithium batteries is almost constantly showing 13.1-13.2V (though once down to 13.0). Plenty of sunlight these days for the solar.But is it the case that this is not indicating the real charge?

Using the battery voltage to judge the state of charge is kind of OK for lead-acid batteries, if you know what you are doing, although it can be misleading. For LiFePO4 batteries it's a complete waste of time.

This is one of the situations where the battery voltage is entirely unrelated to the state of charge. The solar controller is forcing the voltage to 13.1 - 13.2V. The battery will charge at this voltage, but quite slowly. Eventually it will get to 100%.
It's better to read the voltage when it's dark and there's no output from the solar controller. Even then, with LiFePO4 batteries it's not a good indicator of charge state. But at least if it's less than 12.0V you'll know the battery is nearly flat.

 

[Pausim]

This link should take you to some Relion information. https://www.solar-electric.com/lib/wind-sun/Relion_RB100_Specifications.pdf
They do not need 3 phase charging. The rule of thumb voltages you gave do not apply to LiFePO4. A charge rate of 14.6v is recommended if you want them fully charged, a maintenance charge is not needed but 13.8v is suggested if you need to keep other things running.

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[popotla]

This link should take you to some Relion information. https://www.solar-electric.com/lib/wind-sun/Relion_RB100_Specifications.pdf
They do not need 3 phase charging. The rule of thumb voltages you gave do not apply to LiFePO4. A charge rate of 14.6v is recommended if you want them fully charged, a maintenance charge is not needed but 13.8v is suggested if you need to keep other things running.

Thanks for replies.

It's better to read the voltage when it's dark and there's no output from the solar controller. Even then, with LiFePO4 batteries it's not a good indicator of charge state. But at least if it's less than 12.0V you'll know the battery is nearly flat.

The read-out for my lithium batteries is almost constantly showing 13.1-13.2V (though once down to 13.0). This applies whether it's sunny or dark.

Even then, with LiFePO4 batteries it's not a good indicator of charge state. So how can I know the state of charge??

A charge rate of 14.6v is recommended if you want them fully charged, a maintenance charge is not needed but 13.8v is suggested if you need to keep other things running. And how can I CONTROL it? Am I to assume that the system is set up in such a way that it won't overcharge or completely discharge?

I'm using the stuff I'm using (two fridges on minimum cooling, CPAP apparatus without water, blender and mixer, lighting, and the indicated voltage doesn't change. Thus I don't know the state of charge.

 

[Pausim]

@popotla your Relion battery management system will protect the batteries from the voltage extremes that are likely to cause damage. I try to keep to a maximum of 14.6v and a minimum of 12.5v but the real state of charge is difficult to calculate from voltage alone, it depends on the rate of discharge. I reckon your 13v and over is a comfortable place to be so no cause for panic. If you are getting near the limit the votage will start to drop more rapidly and that might be the time to start turning things off.

I also use a CPAP and I don’t want it shutting down at night for want of power. To make sure this doesn’t happen I use a Battery Monitor. This device measures the the amps out and amps in and tells you the % charge left. The Victron BMV700 series has settings for LiFePO4 batteries, which is why I bought one. None of the others seem to be adjustable for the greater efficiency of lithium.

Hope this helps but keep on asking until you are happy with your arrangements.

 

[popotla]

Qtn. 1: So the digital panel which gives readings for starter and o-b batteries and the solar (as well as water-tank levels, and also has switches for 12V, 220-inverter switch and water pump) is an entirely separate animal from a battery monitor?

Qtn.2: What might be the cause of some flashing/flickering in the o-b battery compartment? This happened a couple of times, for a few seconds.

 

[Pausim]

Q1. Yes the battery monitor is a separate bit of kit.

Q2. No idea but you might need to check there are no loose connections.