Thank you sir! Your overcharge protection circuit gave my old misbehaving noisy ("grrrr") hot converter charger some much needed rest. The relay is switching an additional reed relay that is switching a large AC relay (doesn't run from battery power) that is keeping a large AC charger disconnected when it isn't needed (rather than its previous nonstop ccs behavior). With only 22ma draw during float, it can keep the AC charger asleep for days. With that plus a fridge sensor, battery sensor and radio memory, the time is about 2 days. That was the target.
But I also have a solar panel, since the plan is to keep the AC charger asleep by using solar charge just a fraction higher than the AC charger. It is a 30w (max rated) panel. So kicking myself for not choosing a 5w panel that could not overcharge a large battery or a 10w panel easily managed by buck boost card (capacity of the buck boost is higher than the max current of the solar panel), but no, I got a 30w panel that is much harder to manage. . .
Thanks. What component values do you recommend? My battery "idles" at 12.77, easily charges at up to 13.5, begrudgingly goes to 13.8. . . and has accelerated wear when out of this range. It also has accelerated wear when kept to one steady voltage charge but that is not a concern with the solar panel that rests every night. Anyway, I'd like to try your circuit for the solar panel, so what component values to start with, and how to trim?
chargers
i didnt read all of the posts, and if i missed somthing sorry.
where i work we use huge batteries, for backup power at railroad crossings and other sites to allow trains to run even in outage situations.
the chargers we use are made by 2 or 3 diffrent companys.
they are self regulating (float voltages set by users) and will monitor temp.
i can say from experiance, if you take care of the batteries they will last a long time.
look up craig railchargers, and you can see what i am talking about.
i have saved several that have gone "grounded" that no longer are useable on the railroad due to FRA regulations.
send me a pm and ill tell u more.
i didnt read all of the posts, and if i missed somthing sorry.
where i work we use huge batteries, for backup power at railroad crossings and other sites to allow trains to run even in outage situations.
the chargers we use are made by 2 or 3 diffrent companys.
they are self regulating (float voltages set by users) and will monitor temp.
i can say from experiance, if you take care of the batteries they will last a long time.
look up craig railchargers, and you can see what i am talking about.
i have saved several that have gone "grounded" that no longer are useable on the railroad due to FRA regulations.
send me a pm and ill tell u more.
Ah, well, actually, the circuit failed. I suspect the cause of failure was the RV half wave converter/charger output. The battery didn't quite smooth that out as expected. The relay outputted first 6v and then steadily climbed up to 13.6v, plus it was making a lot of chatter and squealing noises. This didn't happen on ordinary DC, so perhaps it could work for solar. Anyway, with the AC charger, the battery ended up not charged at all, and the relay broke from all the chattering. I've no idea where to go from here but it seems that I should try something different for the high amperage AC charger. Help? I need some ideas.
Yes, that is the simplest option if you want to keep the circuit as it is.
Try a 10,000µF for example.
Any residual ripple smaller than the hysteresis will apparently reduce it.
Daniel,
I did not read the whole thread but from the last two pages I gather you have a solar panel. These can have an output of some 18 -22VDC. Normally you do not want to over-charge the battery which should not be allowed to rise above 14.4VDC. The lower cut-off point is 13.4VDC which is the float voltage, both valid at 20 deg C.
This is simply done by a window comparator as mentioned earlier so that when the battery discharges to 13.4V the switch turns on and when the terminal voltage reaches 14.4V it turns off.
The fuller the battery the longer it will take to fall to 13.4V or quicker to reach 14.4V thus the charger is pulsating at the end of charge and so keeps the battery 100% full.
I do not have this schematic at home but will check back tomorrow if there is interested and then I will post it here.
I did not read the whole thread but from the last two pages I gather you have a solar panel. These can have an output of some 18 -22VDC. Normally you do not want to over-charge the battery which should not be allowed to rise above 14.4VDC. The lower cut-off point is 13.4VDC which is the float voltage, both valid at 20 deg C.
This is simply done by a window comparator as mentioned earlier so that when the battery discharges to 13.4V the switch turns on and when the terminal voltage reaches 14.4V it turns off.
The fuller the battery the longer it will take to fall to 13.4V or quicker to reach 14.4V thus the charger is pulsating at the end of charge and so keeps the battery 100% full.
I do not have this schematic at home but will check back tomorrow if there is interested and then I will post it here.
Um? Could you sketch that? I'm not quite sure how to get rid of the pulsing from the converter without also making 18.4vdc. And I've no idea how the battery didn't smooth this out. For dealing with the AC converter/charger, I'm a bit mystified as to how to go about it. The half wave noise cause Elvee's circuit to chatter the relay and the ac content appears on the output. Elvee's circuit could work a solar cell or a constant current DC charger and it tested out well. Perhaps I will have to replace the AC charger; however, it is a useful 10 ampere charger except for the flaws (common to older models) that it puts a lot of heat and noise indoors, nonstop at more than $20 monthly expense on the electric bill. I wanted to change it to go to sleep after charging and then. . .
Hi Nico!
Thank you.
Hopefully that is adjustable since the most modern of marine batteries last longer at a bit lower voltage (max 13.8vdc). Yes, I do also have a solar panel. It is not yet deployed. The idea was to give the AC converter/charger approximately 2 day nap after it charged the battery to ~13.5vdc. . . and then adding the solar panel assures that the 12.6vdc (12.5v to 12.7v) switch on point is rarely reached. That way the AC converter/charger goes to sleep and stays asleep until/unless the load demand (such as from the furnace blower or other heavy load) happens to pull down the battery lower than ~12.6v despite the solar panel.
P.S.
The circuit in post 39 is of interest, but I do not have the skills to guess every one of the unlisted values. It does appear to be adjustable though.
I am surprised at the accuracy of the charging voltage requirement for maintenance charging.
They state
Does the C refer to case temperature, or electrolyte temperature, or plate temperature, or some other?
To obtain precision, it seems that a 10 C degree error uses up more than half of the tolerance for the maintenance charge voltage.
How do we determine the precise Maintenance charge voltage for a particular battery, let's say the one I have on charge in front of me?
They state
and give the temperature correction of -3mV/C.
Does the C refer to case temperature, or electrolyte temperature, or plate temperature, or some other?
To obtain precision, it seems that a 10 C degree error uses up more than half of the tolerance for the maintenance charge voltage.
How do we determine the precise Maintenance charge voltage for a particular battery, let's say the one I have on charge in front of me?
Another charger design question.
I am familiar with the 3stage charging, i.e Constant Current, to Constant Voltage to Maintenance charging. This is relatively easy to design and build without microprocessor controllers.
The Question.
What alternative "analog" solutions are available to detect and change the CV (stg2) mode to M (stg3) mode?
Detect the actual CV mode current and switch over?
Detect/read the time on stg2 and switch over?
Others?
I have always used the 10hr capacity as the CCS charge rate i.e. a 60Ahr battery charged @ 6A for about a day gets upto the CV limit and automatically becomes CV mode, where I leave it for about 2days. I see that many of these links are suggesting much higher rates of charge and that necessarily enforces much shorter charging periods to avoid gassing.
Is my "slow" version of CC then CV doing the battery damage, or is it simply a "safe & reliable" way to charge and maintain longevity? But takes a lot longer?
I am familiar with the 3stage charging, i.e Constant Current, to Constant Voltage to Maintenance charging. This is relatively easy to design and build without microprocessor controllers.
The Question.
What alternative "analog" solutions are available to detect and change the CV (stg2) mode to M (stg3) mode?
Detect the actual CV mode current and switch over?
Detect/read the time on stg2 and switch over?
Others?
I have always used the 10hr capacity as the CCS charge rate i.e. a 60Ahr battery charged @ 6A for about a day gets upto the CV limit and automatically becomes CV mode, where I leave it for about 2days. I see that many of these links are suggesting much higher rates of charge and that necessarily enforces much shorter charging periods to avoid gassing.
Is my "slow" version of CC then CV doing the battery damage, or is it simply a "safe & reliable" way to charge and maintain longevity? But takes a lot longer?
Hi Andrew, this is not misleading at all, float is not a charge cycle, the battery voltage is being maintained during float only.
Equalization charge is used when the battery is fully charged which is after the absorption phase, then the voltage is ellevated for a short period to ensure that any "lazy" cells are equalized.
One can easily see when the battery is 80% fully charged by closely monitoring dV/dt since you will see a rapid increase in battery voltage at that point. This is when you switch to constant voltage and you then either use a fractional timer or you look at the charge current falling to a few mA when the battery is 100% full.
Now you can select to either float or should you want to equalize. Equalize is not performed at every charge cycle only when you suspect that the cells are not equally charged, this can be checked with a voltmeter or better still with a hydrometer.
Hawkins has developed battery charge strategy with most of the major battery manufacturers over a 50 year period. Developing battery charging strategies takes years not a quick calculation.
By not charging a battery correctly you can reduce its life by many cycles, especially deep cycle batteries for stand-by power which is designed to operate for 15 years and can be killed in less than a year.
When batteries die prematurely there are always questions asked as who is to blame is it the charger or is it the battery manufacturer or is it the person maintaining the batteries. Battery manufacturers do not approve every charging campaign available although most people think they are qualified to charge batteries, it is a simple case of connecting a power supply to a battery and whacking the hell out of it as hard and fast they can and you can provided you know what you are doing.
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